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  <xs:element id="hrth_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageRemainingContractualTerm" abstract="false" name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageRemainingContractualTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="hrth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIntrinsicValueAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIntrinsicValueAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="hrth_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodIntrinsicValue" abstract="false" name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodIntrinsicValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_ShareBasedPaymentArrangementOptionExercisePriceRangeOutstandingAndVestedWeightedAverageExercisePrice" abstract="false" name="ShareBasedPaymentArrangementOptionExercisePriceRangeOutstandingAndVestedWeightedAverageExercisePrice" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="hrth_QualifiedPlanIMember" abstract="true" name="QualifiedPlanIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_QualifiedPlanIIMember" abstract="true" name="QualifiedPlanIIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanNumberOfPlans" abstract="false" name="DefinedBenefitPlanNumberOfPlans" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanTerminationTerm" abstract="false" name="DefinedBenefitPlanTerminationTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanCashPaymentTerminationAmount" abstract="false" name="DefinedBenefitPlanCashPaymentTerminationAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanAmortizationPeriod" abstract="false" name="DefinedBenefitPlanAmortizationPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanPeriodToMeetGoals" abstract="false" name="DefinedBenefitPlanPeriodToMeetGoals" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanPeriodOfOperatingHistoryAndSufficientTradingVolumeOfInvestedEntity" abstract="false" name="DefinedBenefitPlanPeriodOfOperatingHistoryAndSufficientTradingVolumeOfInvestedEntity" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanOtherSecuritiesInvestmentMember" abstract="true" name="DefinedBenefitPlanOtherSecuritiesInvestmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember" abstract="true" name="DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_EmergingMarketsMember" abstract="true" name="EmergingMarketsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_InvestmentGradeMember" abstract="true" name="InvestmentGradeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_CashEquivalentMember" abstract="true" name="CashEquivalentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_DefinedBenefitPlanExpectedFutureBenefitPayments" abstract="false" name="DefinedBenefitPlanExpectedFutureBenefitPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_ForeignSubsidiaryDividendInclusions" abstract="false" name="ForeignSubsidiaryDividendInclusions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_EffectiveIncomeTaxRateReconciliationReturnToProvisionAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationReturnToProvisionAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_EffectiveIncomeTaxRateReconciliationAdjustmentsToStateAttributes" abstract="false" name="EffectiveIncomeTaxRateReconciliationAdjustmentsToStateAttributes" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DeferredCompensationAndRetirementPlan" abstract="false" name="DeferredCompensationAndRetirementPlan" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DeferredTaxAssetsLeasesLiability" abstract="false" name="DeferredTaxAssetsLeasesLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DeferredTaxLiabilitiesDeferredCompensationAndBenefits" abstract="false" name="DeferredTaxLiabilitiesDeferredCompensationAndBenefits" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DeferredTaxLiabilitiesRightOfUseAssets" abstract="false" name="DeferredTaxLiabilitiesRightOfUseAssets" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_DisallowedBusinessInterestExpenseCarryforwardsNotSubjectToExpiration" abstract="false" name="DisallowedBusinessInterestExpenseCarryforwardsNotSubjectToExpiration" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_RestructuringAndRelatedCostNumberOfMeetingsMinimum" abstract="false" name="RestructuringAndRelatedCostNumberOfMeetingsMinimum" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="hrth_RestructuringAndRelatedCostCostReductions" abstract="false" name="RestructuringAndRelatedCostCostReductions" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_ConsultingFeesMember" abstract="true" name="ConsultingFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="hrth_FacilityAssetImpairmentAndOtherExpenseMember" abstract="true" name="FacilityAssetImpairmentAndOtherExpenseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_LeaseImpairmentAndTerminationChargesMember" abstract="true" name="LeaseImpairmentAndTerminationChargesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_CapitalLossesFromAssetDisposalMember" abstract="true" name="CapitalLossesFromAssetDisposalMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="hrth_ContributionMargin" abstract="false" name="ContributionMargin" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="hrth_EBITDA" abstract="false" name="EBITDA" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
