C. W. Trigg, C. W. Dodge and L. F. Meyers, Comments on Problem 133, Eureka (now Crux Mathematicorum) 2, no. 7 (August--September 1976) 144--150. Problem 133 is the problem, proposed by K. S. Williams, who said he was shown it by one of his students. C. W. Trigg gives a good history of the problem.
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