public Parser dataReference() {
        if (dataReferenceParser == null) {
           FutureParser future = scoped("dataReference");
           dataReferenceParser = future;
           future.setParser(
               sequence(
                   optional(
                       sequence(
                           optional(
                               token("BY")
                           ),
                           token("REFERENCE")
                       )
                   ),
                   plus(
                       choice(
                           token("ANY"),
                           sequence(
                               optional(
                                   token("OPTIONAL")
                               ),
                               dataName(),
                               optional(
                                   sequence(
                                       token("DELIMITED"),
                                       optional(
                                           sequence(
                                               token("BY"),
                                               token("SIZE")
                                           )
                                       )
                                   )
                               ),
                               optional(
                                   sequence(
                                       token("AS"),
                                       typeName(),
                                       optional(
                                           attributeClause()
                                       )
                                   )
                               )
                           ),
                           typedefName()
                       )
                   )
               )
           );
        }

        return dataReferenceParser;
    }