Letters must include all of the following information:
the specific period of your employment with the company
the positions you have held during the period of employment and the time spent in each position
your main responsibilities in each position
your total annual salary plus benefits
the signature of your immediate supervisor or the personnel officer of the company
a business card of the person signing
可是我工作证明的公证已经做了呀...难道要重做一次吗?