C.J. Colbourn & D. Jungnickel 
Designs and Graphs [PDF ebook] 

In 1988, the news of Egmont Khler’s untimely death at the age of 55reached his friends and colleagues. It was widely felt that a lastingmemorial tribute should be organized. The result is the present volume, containing forty-two articles, mostly in combinatorial design theory andgraph theory, and all in memory of Egmont Khler. Designs and graphswere his areas of particular interest; he will long be remembered for hisresearch on cyclic designs, Skolem sequences, t-designs and the Oberwolfach problem. Professors Lenz and Ringel give a detailedappreciation of Khler’s research in the first article of thisvolume.There is, however, one aspect of Egmont Khler’s biographythat merits special attention. Before taking up the study of mathematics atthe age of 31, he had completed training as a musician (studying bothcomposition and violoncello at the Musikhochschule in Berlin), and workedas a cellist in a symphony orchestra for some years. This accounts for hisinterest in the combinatorial aspects of music. His work and lectures inthis direction had begun to attract the interest of many musicians, and hehad commenced work on a book on mathematical aspects of musical theory. Itis tragic indeed that his early death prevented the completion of his work;the surviving paper on the classification and complexity of chordsindicates the loss that his death meant to the area, as he was almostuniquely qualified to bring mathematics and music together, being aprofessional in both fields.