1. Combinatorics of Permutations;Bóna,2004
2. Combinatorial Matrix Classes;Brualdi,2006
3. Combinatorial Matrix Theory;Brualdi,1991
4. D. Eppstein, Nonrepetitive paths and cycles in graphs with application to Sudoku, 2005, arXive:cs/0507053.
5. Unwed numbers – the mathematics of Sudoku a puzzle that boastsNo math required;Hayes;Amer. Sci.,2006