ENSLEY, Douglas E. - CRAWLEY, J. Winston. Discrete mathematics : mathematical reasoning and proof with puzzles, patterns, and games. Hoboken, NJ : Wiley, c2006, [vyd.] 2005. xii, 691 s. Dostupné na internetu: <http://www.gbv.de/du/services/agi/E475DFCCE9FD818CC125717D0050A05A/000000016322717> <http://www.loc.gov/catdir/toc/ecip0514/2005017417.html> <http://www.loc.gov/catdir/enhancements/fy0622/2005017417-d.html> <http://www.loc.gov/catdir/enhancements/fy0653/2005017417-b.html> ISBN 0-471-47602-1.