1. Algorithm 306, Permutations with repetitions;Bratley;Comm. ACM,1967
2. On the analytical forms called trees;Cayley,1891
3. Algorithm 383, Permutations of a set with repetitions;Chase;Comm. ACM,1970
4. Algorithmic Combinatorics;Even,1973
5. A.S. Fraenkel and M. Mor, Combinatorial compression and partitioning of large dictionaries, Computer J., to appear.