Averbach, Bonnie; Chein, Orin (1980), Problem Solving Through Recreational Mathematics, Dover, p. 195, ISBN 9780486131740. 9780486131740
Sloane, N. J. A. (ed.). "Sequence A033996". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. /wiki/Neil_Sloane
Averbach, Bonnie; Chein, Orin (1980), Problem Solving Through Recreational Mathematics, Dover, p. 195, ISBN 9780486131740. 9780486131740
Watkins, John J. (2004), Across the Board: The Mathematics of Chessboard Problems. Paradoxes, perplexities, and mathematical conundrums for the serious head scratcher, Princeton University Press, pp. 44, 68, ISBN 978-0-691-15498-5. 978-0-691-15498-5
Watkins, John J. (2004), Across the Board: The Mathematics of Chessboard Problems. Paradoxes, perplexities, and mathematical conundrums for the serious head scratcher, Princeton University Press, pp. 44, 68, ISBN 978-0-691-15498-5. 978-0-691-15498-5