I've listed the cover page of my H1 extension,雇主的工作證明 here is the petition letter from your company, similar to the one when they apply H1 for you at the first time.
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1.Form I-129 and separate sheet for Question 7 & 9 of Part 4.
2.Certified Form ETA 9035E;
3.Employer’s letter in support of petition;
4.Copy of Beneficiary’s passport, visa, H-1B approval notice and I-94;
5.Copy of Beneficiary’s I-20 and OPT;
6.Copy of Beneficiary’s certificate and tran from xxx University;
7.Copy of Beneficiary’s W-2 Form for the past three years and recent pay-stubs;
8.Copy of Beneficiary’s resume;
9.Information about the Petitioner;
10.Company check payable to USCIS in the amount of $1690.