In the mid-1970s, Selberg gave a lecture at one of Rockefeller University's "Number Theory Days" under the general heading of spectral theory and equidistribution properties of discrete groups. The same material was included in a lecture at Stanford in 1980. Following his passing in 2007, several (European A4-size) lecture transparencies on this theme plus a number of loosely organized, much older-looking, cognate working papers were found in Selberg's office. The files below are scans of this material.
File 1 shows the transparencies: these may well have formed part of one of Selberg's 1991 Tel Aviv lectures (cf. the corresponding 'bullet' one level up, under Tel Aviv abstracts). Files 2 through 4 (scanned from American-sized pages) appear to be from the 1970s; file 5 (from a bit newer, A4-size) is less clear.
The last page of file 2 was found mixed in among papers on a completely different topic. It is now presumably back in the right place.