Graduate course taught at the University of California, Berkeley. From the front matter: "Transcribed from tapes by Katherine Turner. Tapes on file with the Language Laboratory, University of California, Berkeley. Lectures on Sept. 28, Nov. 1, and Dec. 2 not recorded". 542 pages. See digitized versions of the tapes in Series 10 of this collection.
Andrew Garrett talks about lanugage diversity, specifically in Indo-European languages.; Proceedings of the American Philosophical Society. Vol. 161, No. 1 (March 2017) pp. 25-38.