a.m.=above mentioned.都是一些不规范用法.
我遇到的例子：Regarding your a.m.PO please note that there will be a delay in delivery.New delivery date is 47.CW 2012.Please accept our apologies for any inconvenience.英国人,美国人不这么写.都是些非英语国家的欧洲人这么写.