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