Professor Donald Solitar, eminent mathematician, occasional poet and one of York's originals, died unexpectedly on April 25.
Prof. Solitar came to York in 1968 from the Polytechnic University of New York to head the Department of Mathematics, Faculty of Arts. He also served as the acting chair of the Computer Science Department from 1968 to 1973. Through his efforts and those of his close friend and collaborator Abe Karrass, York's Department of Mathematics soon became a world centre in combinatorial group 
theory (the study of groups – which in essence measure the symmetries of objects both real and imaginary – in terms of generating symmetries and relations between them).
Right: Prof. Donald Solitar in a photograph taken in 1975. Photograph by Roy Nicholls.
Prof. Solitar was well known in the international mathematical community, in particular for the now classic book Combinatorial Group Theory (2004), written jointly with his adviser Wilhelm Magnus and with Abe Karrass. The book was subsequently translated into Russian. In 1982, Prof. Solitar was elected a Fellow of the Royal Society of Canada.
Regarded as an inspirational teacher, he received an Ontario Confederation of University Faculty Associations (OCUFA) Teaching Award in 1985. He had an ebullient and, in other ways, extraordinary personality, and was extremely generous to all he came in contact with.
He is survived by his wife Francien, his sister Miriam, and a large extended family of which he was the patriarch.