Dr. Nathaniel H. Leff was a professor of Economics at Columbia University Business School for over twenty-five years. Among his published books are two volumes on "Underdevelopment and Development in Brazil" which is being translated in Portuguese and taught in Brazilian Universities. A reporter for a Brazilian newspaper wrote a fascinating article about Dr. Leff's academic influence. Here is a summary of Dr. Nathaniel Leff's academic career: https://prabook.com/web/nathaniel.leff/953812
For years, Nosson Chayim Leff wrote a weekly "email on the Sfas Emes" (available here), and finally wrote a sefer, Emes Ve'emunah, A Sfas Emes Companion, published by Menucha publishers.
Dr. Leff and Nosson Chayim Leff were the same person.
He had a very positive influence on many people through his multi-faceted personality. We are looking for stories from people who interacted with Dr. Leff, to share within the family or to post on this website.