A very long letter to Zalman Shazar, where the Rebbe discusses the Yud-Beis Tammuz farbrengen, the power of direct influence, the importance of continuing agriculture in Kfar Chabad, housing for Torah students in Jerusalem, publishing the Alter Rebbe’s works, and concludes with hope for spiritual renewal during the Three Weeks.
https://www.torahrecordings.com/rebbe/igroskodesh/015/012/5629