In the last ten years the problem has forsaken its underground
existence by appearing in various forms as a problem in books and journals,
sometimes without attribution as an unsolved problem.
Prizes have been offered for its solution:
$50 by H. S. M. Coxeter in 1970, then
$500 by Paul Erdös, and more recently 1000 by B. Thwaites .
Over twenty research articles have appeared on the problem and related problems.
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