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The Design and Implementation series of books, which he co-authored, are regarded as very high quality works in computer science.They have been strongly influential in the development of the BSD descendants and have contributed to their cohesive and well-thought-out nature.
S. Leffler, M. McKusick, M. Karels, J. Quarterman: The Design and Implementation of the 4.3BSD UNIX Operating System, Addison-Wesley, January 1989, ISBN 0-201-06196-1. German translation published June 1990, ISBN 3-89319-239-5. Japanese translation published June 1991, ISBN 4-621-03607-6 (out of print).
S. Leffler, M. McKusick: The Design and Implementation of the 4.3BSD UNIX Operating System Answer Book, Addison-Wesley, April 1991, ISBN 0-201-54629-9. Japanese translation published January 1992, ISBN 978-4-8101-8039-8