Should ask HR to sign all the forms and letters. HR might ask permission from your supervisor, though. The ref letter from your current supervisor should be useful. Especially to emphasize how important you are and how important your current project is. and als provide some information as soft evidence.
c*r
4 楼
谢谢你的回答。 读博士时候的老板的推荐信有作用么?
r*a
5 楼
1. Either one is fine. But it depends on how the petition letter is phrased. 2. 导师的推荐信is fine as long as it is a positive letter of recommendation. Otherwise do not use it. Try not to have more than 2 letters from one organization. It would be helpful the locations of your recommenders are widely spreaded internationally (at least in USA if not globally). Good luck!