if (returnCalculatorName == null || returnCalculatorName.isEmpty() || returnCalculatorName.size() != 1) {
return null;
}
final Set<ValueRequirement> requirements = new HashSet<ValueRequirement>();
requirements.add(new ValueRequirement(REQUIREMENT_NAME, target.toSpecification()));
final UnderlyingTimeSeriesProvider timeSeriesProvider = new UnderlyingTimeSeriesProvider(OpenGammaCompilationContext.getHistoricalTimeSeriesResolver(context), _resolutionKey,
context.getSecuritySource());
requirements.add(timeSeriesProvider.getSeriesRequirement(GREEK, (FinancialSecurity) target.getPosition().getSecurity(), DateConstraint.VALUATION_TIME.minus(samplingPeriodName.iterator().next()),
DateConstraint.VALUATION_TIME));
return requirements;
}