Cataloging has recently been completed on the Harvard Theatre Collection’s Tennessee Williams Additional Papers, 1946-1983, ( MS Thr 550.) Details can be found in the finding aid created by senior manuscripts cataloger Bonnie B. Salt.
These papers join a wealth of Tennessee Williams material at the Houghton Library and the Harvard Theatre Collection, most notably the 
Tennessee Williams papers, 1932-1983 (MS Thr 397.)