回复：LABOR 申请求助!

以前的同事上司都可以，即使现在已离职退休也无妨现在职的，用公司的信函并最好附上名片，现离职的附上地址电话。

1) 信中必须交代你们之间的关系，共事的时间

2) 正如toosad所说，尽量多劳工卡申请书上的keyword，要让外行(高中文化程度的移民官)也能看得懂并相信。

3) 必须前后一致，能自圆其说，经得住RFE。要与你之前H-1申请时递过的job experience resume上一致。如果大学学的是物理专业，而毕业后的工作从事的是化学，万一遇到个较真的移民官，你要能够解释。

附上我用的letter (刚批了I-140在TSC EB2 RIR)，供参考。

Dear Sir or Madam:

This letter will verify experience obtained by Mr.也想移民美国 during his employment at ABC Company. I was previous employed by ABC Company in the position of manager in Technical Support Department during 6/1991 to 8/2000.
During 4/1996 to 7/1999, Mr.也想移民美国worked under my supervision in the position of IT Technical Specialist, Database Management Assistance Engineer,
Software Quality Assurance Engineer and Network Chain Store data Analyst. His detailed job duties including:

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2...
3...

Mr.也想移民美国 was employed in a full-time position as a consultant with ABC Company

Sincerely