organisation letterhead, where possible (我认为这个是可有可无的)
certified copy of original (这个是公证啥?)
employer/s signature (推荐人签名)
position title for each role. ( 每个职位的title)
period of employment for each role (时间)
list full job duties for each role (每个职位的职责)
Supervisor/manager details (这个如何去表达?)