The distribution of 3 x + 1 trees. Applegate, David; Lagarias, Jeffrey C. — 1995 Experimental Mathematics
On the solution of traveling salesman problems. Applegate, David; Bixby, Robert; Chvátal, Vašek; Cook, William — 1998 Documenta Mathematica
Sloping binary numbers: a new sequence related to the binary numbers. Applegate, David; Cloitre, Benoit; Deléham, Philippe; Sloane, N.J.A. — 2005 Journal of Integer Sequences [electronic only]