Here is a sample reference of an good student Harvard would accept:
X has been an assistant in my laboratory during the past year, and has proven to be exceptional in several respects. First, X is exceptionally intelligent. He proved to be a very quick study, learning the elements of experimental design and the uses of microcomputers in record time. Furthermore, his questions are always thoughtful and penetrating. X threw himself into his assigned projects wholeheartedly, and shows every sign of having real talent in . . . . I was a little surprised by his high degree of enthusiasm because I knew that X was not primarily interested in . . . . When I mentioned this to him, I discovered that he has well defined career goals that mesh with the projects he was working on . . . .
Second, X is exceptionally diligent and hard working. He worked many extra hours over the summer. I vividly recall coming into the lab late in the evening. . . and finding X at work. X invariably finished projects well in advance of our projected target date. X was always cheerful during this intense period, and was a joy to have in the lab.
Third, X is very good at working with other people. He is exceptionally nice and considerate and sensitive. X is not only good humored and friendly, but also is good at gauging other people’s level of knowledge and attitudes. . . .
All in all, I think X has a very bright future, and I am sure that he would benefit from . . . . Given his great intelligence and sensitivity, I am sure that he could put . . . to good use.
In short, I give X my highest recommendation, and very much hope that the committee judges his application favorably.