1. A characterization of the Bell numbers;Aigner;Discrete Math.,1999
2. Juggling drops and descents;Buhler;Amer. Math. Monthly,1994
3. A note on the binomial drop polynomial of a poset;Buhler;J. Combin. Theory Ser. A,1994
4. q-Bernoulli numbers and polynomials;Carlitz;Duke Math. J.,1948
5. Eine Charakterisierung der q-Exponentialpolynome;Cigler;Österreich. Akad. Wiss. Math.-Natur. Kl. Sitzungsber. II,1999