code: @Override
  	public Response checkIsMember(String CorpNum, String LinkID)
  			throws PopbillException {
  
  		return httpget("/Join?CorpNum=" + CorpNum + "&LID=" + LinkID, null,
  				null, Response.class);
  	}
docs: /* (non-Javadoc)
  @see com.popbill.api.BaseService#checkIsMember(java.lang.String, java.lang.String)