code: @Override
  	public HTTaxinvoiceXMLResponse getXML(String CorpNum, String NTSConfirmNum)
  			throws PopbillException {
  		return getXML(CorpNum, NTSConfirmNum, null);
  	}
docs: /*
  (non-Javadoc)
  @see com.popbill.api.HTTaxinvoiceService#GetXML(java.lang.String, java.lang.String)