What has the author W F Clocksin written?

You're likely thinking of W. F. Clocksin, a British computer scientist. He is known for co-authoring the book "Programming in Prolog" with C. S. Mellish. This book, published in 1981, was one of the first and most influential textbooks on the programming language Prolog.

It's worth noting that "W. F. Clocksin" appears to be the full name used in the book, although it is not uncommon to see him credited as "William Clocksin" in other publications.

While the book on Prolog is his most well-known work, he may have other publications as well.