1. M. Abramowitz, I. Stegun, Handbook of mathematical functions with formulas, graphs and mathematical tables, in: Applied Mathematics Series, vol. 55, US Govt. Printing Office, Washington, 1964.
2. Motzkin numbers;Aigner;Eur. J. Combinatorics,1998
3. Bell numbers, log-concavity, and log-convexity;Asai;Acta Appl. Math.,2000
4. Generalized permutation patterns and a classification of the Mahonian statistics;Babson;Séminaire Lotharingien de Combinatoire,2000
5. E. Barcucci, R. Pinzani, R. Sprugnoli, The Motzkin family, in: P.U.M.A. Series A, vol. 2, 1991, pp. 249–279.