The Rebbe thanks for the sent pages from Chakal Yitzchak and responds with a Purim kuntres. He expresses appreciation for details about the Baal HaTanya's passing and requests more, noting the scarcity of accurate information. He also references a teaching of the Mitteler Rebbe on Purim connected to a complex debate in Chassidus.
https://www.torahrecordings.com/rebbe/004_igros_kodesh/adar_beis/952