Shorter strings containing all k-element permutations

Adleman, 1974, Short permutation strings, Discrete Mathematics, 10, 197, 10.1016/0012-365X(74)90116-2 Open Garden Forum Vašek Chvátal, David A. Klarner, Donald E. Knuth, Selected combinatorial research problems, Technical Report 292, Stanford University, 1972. Galbiati, 1976, On permutation embedding sequences, SIAM Journal of Applied Mathematics, 30, 421, 10.1137/0130040 Koutas, 1975, Shortest string containing all permutations, Discrete Mathematics, 11, 125, 10.1016/0012-365X(75)90004-7 Mohanty, 1980, Shortest string containing all permutations, Discrete Mathematics, 31, 91, 10.1016/0012-365X(80)90177-6 Malcolm Newey, Notes on a problem involving permutations as subsequences, Technical Report 340, Stanford University, 1973. Savage, 1982, Short strings containing all k-element permutations, Discrete Mathematics, 42, 281, 10.1016/0012-365X(82)90224-2