@book{109641,
	author = {Allenby, R. B. J. T. and Slomson, A. B.},
	title = {How to count :},
	publisher = {CRC Press,},
	year = {2011.},
	series = {Discrete mathematics and its applications},
	address = {Boca Raton, FL :},
	edition = {2nd ed.},
	note = {First published as: an introduction to combinatorics, 1991.}
}