My categoty is EB1b which is outstanding researcher sponsored by the employer. The first RFE required basically five big items besides employment letter, my Ph.D degree certificate, W2 form...The five big items include more recommendation letters writen by people who never worked with me before, jornal ranking (international circulation, reprints....), evidence showing that I have had more than three years teaching experience ( it was written by my boss), journal citation, membership qualification, and evidence of being an outstanding researcher (internationally recognized....).