For EB1 Outstanding Professor or Researcher (EB-1B) petition, the documentation should be submitted to USCIS to prove that the alien beneficiary is an internationally recognized outstanding professor or researcher. The petition should also establish that the alien beneficiary has three years of research or teaching experience in the academic field. 

If the experience was gained while pursuing the advanced degree required for the offered position, such experience must be proven to be outstanding. Therefore, experience in teaching or research while working on an advanced degree will be acceptable by USCIS only if the alien has acquired the degree, and if the teaching duties were such that he or she had full responsibility for the class taught, or if the research conducted toward the degree has been recognized within the academic field as outstanding.

The EB1 Outstanding Professor or Researcher regulations specify that evidence of teaching or research experience should be in the form of letters from current or former employers, and should include the name, address, and title of the writer, and a specific description of the duties performed by the foreign national.