GetCustomerRefData ( parameter list ) : CustomerRefData
Returns relevant reference data in accordance with the parameter list. 
In addition to the current valid reference data the next valid reference data, if any, is returned.
Parameters:
All parameters are optional. The following parameters are supported:
- customerId : CustomerId
 Returns only reference data for this customer. If not used, returns data for all relevant customers.
- onlyUpdatedAfter : DateTimeUTC
 Returns only reference data that is updated after "onlyUpdatedAfter".
Returns: