Though reference letters alone are not sufficient to create a good achievement-based petition, they are an important component to showing an applicant's accomplishments in his or her field. We use these letters to put the documentary evidence in context and explain how the applicant's achievements have had an impact on the field as a whole. Reference letters are equally important for EB1, NIW, and O-1 petitions. It is not enough for a letter to make general statements about an applicant's good qualities. The letters must specifically discuss the applicant's contributions to the field in a manner that speaks to their significance.