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    <link:label id="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_C371111ACB3B229C6CA685B964A98D7E_terseLabel_en-US" xlink:label="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_6479B5FE794F5147B0E220CDE9FF93A3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock-Based Compensation</link:label>
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    <link:label id="lab_us-gaap_StatementOfCashFlowsAbstract_26931B1C5A98692B424049FBE2711B63_label_en-US" xlink:label="lab_us-gaap_StatementOfCashFlowsAbstract_26931B1C5A98692B424049FBE2711B63" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Cash Flows [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="loc_us-gaap_StatementOfCashFlowsAbstract_26931B1C5A98692B424049FBE2711B63" xlink:type="locator" />
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    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_53C2D934DC4F9CA4D1FE49FBE271BB9E_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_53C2D934DC4F9CA4D1FE49FBE271BB9E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Operating activities:</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_53C2D934DC4F9CA4D1FE49FBE271BB9E_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_53C2D934DC4F9CA4D1FE49FBE271BB9E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_53C2D934DC4F9CA4D1FE49FBE271BB9E" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ProfitLoss_5D01B620C0FE5F099FB149FBE2729916_verboseLabel_en-US" xlink:label="lab_us-gaap_ProfitLoss_5D01B620C0FE5F099FB149FBE2729916" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Net income (loss)</link:label>
    <link:label id="lab_us-gaap_ProfitLoss_5D01B620C0FE5F099FB149FBE2729916_label_en-US" xlink:label="lab_us-gaap_ProfitLoss_5D01B620C0FE5F099FB149FBE2729916" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_5D01B620C0FE5F099FB149FBE2729916" xlink:type="locator" />
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    <link:label id="lab_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_6A394553CE35E651726A49FBE272F8E5_terseLabel_en-US" xlink:label="lab_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_6A394553CE35E651726A49FBE272F8E5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Adjustments to reconcile net (loss) income to cash (used for) provided by operating activities:</link:label>
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    <link:label id="lab_us-gaap_DepreciationDepletionAndAmortization_5EF253B474B886F7E5CB4A4434BBC120_label_en-US" xlink:label="lab_us-gaap_DepreciationDepletionAndAmortization_5EF253B474B886F7E5CB4A4434BBC120" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Depreciation, Depletion and Amortization</link:label>
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    <link:label id="lab_us-gaap_ShareBasedCompensation_6DDAD8DCA6C47F59376A49FBE272DD34_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensation_6DDAD8DCA6C47F59376A49FBE272DD34" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock-based compensation</link:label>
    <link:label id="lab_us-gaap_ShareBasedCompensation_6DDAD8DCA6C47F59376A49FBE272DD34_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensation_6DDAD8DCA6C47F59376A49FBE272DD34" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation</link:label>
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    <link:label id="lab_us-gaap_DeferredIncomeTaxExpenseBenefit_95C7F28C70A77F25C0A049FBE272EAB1_label_en-US" xlink:label="lab_us-gaap_DeferredIncomeTaxExpenseBenefit_95C7F28C70A77F25C0A049FBE272EAB1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Income Tax Expense (Benefit)</link:label>
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    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssets_DF151F7FA6B9B58AA9EA49FBE27470EA_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssets_DF151F7FA6B9B58AA9EA49FBE27470EA" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Increase in other current assets</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssets_DF151F7FA6B9B58AA9EA49FBE27470EA_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingAssets_DF151F7FA6B9B58AA9EA49FBE27470EA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Other Operating Assets</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_DF151F7FA6B9B58AA9EA49FBE27470EA" xlink:type="locator" />
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    <link:label id="lab_us-gaap_IncreaseDecreaseInAccountsPayable_B2A5B4D173744B8EAC9349FBE2748F33_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInAccountsPayable_B2A5B4D173744B8EAC9349FBE2748F33" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Decrease in accounts payable</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_165EA533F56B6EB636E849FBE274DDE3" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_165EA533F56B6EB636E849FBE274DDE3" xlink:to="lab_us-gaap_IncreaseDecreaseInAccruedLiabilities_165EA533F56B6EB636E849FBE274DDE3" xlink:type="arc" />
    <link:label id="lab_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase in income taxes payable</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Income Taxes Payable</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882" xlink:to="lab_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_36E6B27E3B2A659D3FB449FBE274A882" xlink:type="arc" />
    <link:label id="lab_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Increase in deferred pension and postretirement benefits</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations" xlink:label="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256" xlink:to="lab_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_A70079EF2CB69A7297A149FBE274D256" xlink:type="arc" />
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC_terseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">(Decrease) increase in other long-term liabilities</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Other Noncurrent Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC" xlink:to="lab_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_0FECF9D16C22F8D19E1149FBE27557AC" xlink:type="arc" />
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Other, net</link:label>
    <link:label id="lab_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822_label_en-US" xlink:label="lab_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Increase (Decrease) in Other Operating Assets and Liabilities, Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822" xlink:to="lab_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_B1FEDA8940EA41F0D83449FBE2753822" xlink:type="arc" />
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA_totalLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Cash (used for) provided by operating activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Cash Provided by (Used in) Operating Activities, Continuing Operations</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA" xlink:to="lab_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_06ED916F4D97C2A8724549FBE27524CA" xlink:type="arc" />
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21_terseLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investing activities:</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Cash Provided by (Used in) Investing Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21" xlink:to="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_B85727255D3300F2E7CA49FBE2759D21" xlink:type="arc" />
    <link:label id="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_97CB635B3FD5E51E207649FBE276F62D_negatedLabel_en-US" xlink:label="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_97CB635B3FD5E51E207649FBE276F62D" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Capital expenditures</link:label>
    <link:label id="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_97CB635B3FD5E51E207649FBE276F62D_label_en-US" xlink:label="lab_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_97CB635B3FD5E51E207649FBE276F62D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payments to Acquire Property, Plant, and Equipment</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_97CB635B3FD5E51E207649FBE276F62D" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_7319BA7894D7DE741DEF49FBE276B964_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_7319BA7894D7DE741DEF49FBE276B964" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Proceeds from disposition of capital assets</link:label>
    <link:label id="lab_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_7319BA7894D7DE741DEF49FBE276B964_label_en-US" xlink:label="lab_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_7319BA7894D7DE741DEF49FBE276B964" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from Sale of Property, Plant, and Equipment</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_7319BA7894D7DE741DEF49FBE276B964" xlink:type="locator" />
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    <link:label id="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_FFAAB2D40A058CC4058449FBE2769916_totalLabel_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_FFAAB2D40A058CC4058449FBE2769916" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Cash used for investing activities</link:label>
    <link:label id="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_FFAAB2D40A058CC4058449FBE2769916_label_en-US" xlink:label="lab_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_FFAAB2D40A058CC4058449FBE2769916" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Cash Provided by (Used in) Investing Activities, Continuing Operations</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_FFAAB2D40A058CC4058449FBE2769916" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_8989E417803EE6FFF52749FBE2766C53" xlink:type="locator" />
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    <link:loc xlink:href="nx-20190131.xsd#nx_SellCADMember" xlink:label="loc_nx_SellCADMember_67D1507735EEEC5110564AA0B8021DCE" xlink:type="locator" />
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    <link:label id="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B_terseLabel_en-US" xlink:label="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Sell GBP, buy USD</link:label>
    <link:label id="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B_label_en-US" xlink:label="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sell GBP [Member]</link:label>
    <link:label id="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B_documentation_en-US" xlink:label="lab_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Sell GBP [Member]</link:label>
    <link:loc xlink:href="nx-20190131.xsd#nx_SellGBPMember" xlink:label="loc_nx_SellGBPMember_877B738944751FF6D84B4AA0B802DE7B" xlink:type="locator" />
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    <link:label id="lab_nx_BuyEurSellGbpMember_8DDDA212B4E424823B4E4AA0B802A93D_terseLabel_en-US" xlink:label="lab_nx_BuyEurSellGbpMember_8DDDA212B4E424823B4E4AA0B802A93D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Buy EUR, sell GBP</link:label>
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    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_1EC6DA66F6EA853B2B860CC25348579A" xlink:to="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_1EC6DA66F6EA853B2B860CC25348579A" xlink:type="arc" />
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    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_437207CFD0FB37AE3B870CC253484608_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_437207CFD0FB37AE3B870CC253484608" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_437207CFD0FB37AE3B870CC253484608" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_437207CFD0FB37AE3B870CC253484608" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_437207CFD0FB37AE3B870CC253484608" xlink:type="arc" />
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A53073FA0CBF7B4A59CF0CC253495CF9_terseLabel_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A53073FA0CBF7B4A59CF0CC253495CF9" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Exercisable at end of period</link:label>
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A53073FA0CBF7B4A59CF0CC253495CF9_label_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A53073FA0CBF7B4A59CF0CC253495CF9" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A53073FA0CBF7B4A59CF0CC253495CF9" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_6CB34FFC9DCA2054D6BA0CC2534B7222_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_6CB34FFC9DCA2054D6BA0CC2534B7222" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total intrinsic value of options exercised</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_6CB34FFC9DCA2054D6BA0CC2534B7222" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_6CB34FFC9DCA2054D6BA0CC2534B7222" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_6CB34FFC9DCA2054D6BA0CC2534B7222" xlink:type="arc" />
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA_terseLabel_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair value of stock options vested</link:label>
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA_label_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA" xlink:to="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_C1C80585B511141587840CC2534BA9CA" xlink:type="arc" />
    <link:label id="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_34E4036F036E2EE38B430CC2534BCFA8_terseLabel_en-US" xlink:label="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_34E4036F036E2EE38B430CC2534BCFA8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized compensation cost - non vested stock options</link:label>
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    <link:label id="lab_us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease_7EFBE8B5F2F74613B2BC0CE3C5090AA8_terseLabel_en-US" xlink:label="lab_us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease_7EFBE8B5F2F74613B2BC0CE3C5090AA8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Standard and Extended Product Warranty Accrual, Increase (Decrease) for Preexisting Warranties</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease" xlink:label="loc_us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease_7EFBE8B5F2F74613B2BC0CE3C5090AA8" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_60AC6E3058A181D80A2D0BD7E44AC289" xlink:type="locator" />
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