code: @Override
  	public String getViewURL(String CorpNum, MgtKeyType KeyType, String MgtKey) throws PopbillException {
  		return getViewURL(CorpNum, KeyType, MgtKey, null); 
  	}
docs: /*
  (non-Javadoc)
  @see com.popbill.api.TaxinvoiceService#getViewURL(java.lang.String, com.popbill.api.taxinvoice.MgtKeyType, java.lang.String)