public Parser displayStatement() {
        if (displayStatementParser == null) {
           FutureParser future = scoped("displayStatement");
           displayStatementParser = future;
           future.setParser(
               sequence(
                   token("DISPLAY"),
                   choice(
                       displayTerminalFormat(),
                       displayDeviceFormat()
                   ),
                   optional(
                       token("END-DISPLAY")
                   )
               )
           );
        }

        return displayStatementParser;
    }