Frank E.A. Sander, a longtime Harvard Law School professor known as a mentor to many and a pioneer in the field of alternative dispute resolution, died Feb. 25. He was 90 years old and lived in Cambridge, Massachusetts.

Sander served on the Harvard faculty from 1959 to 2006, authored numerous books on ADR, taught the topic at Harvard and had a profound impact on those who knew him, worked with him and learned from him.