Mathematical Models for Step Sizes by Steven Morrell illustrates some of the ideas behind Optima numbers. There are several programs to calculate Optima numbers on the Misc Corewar Software page.
A Numeric Approach to Diversity Hills by Achille Astolfi.
Categorizing Corewar Warriors - a PowerPoint presentation by Nenad Tomašev and Doni Pracner
Core Wars Genetics: The Evolution of Predation by John Perry is an early paper discussing techniques to evolve competitive warriors.
Evolving Core Warriors by Dave Hillis.
Evolving Warriors by Linus Thorsell.
Ryan Coleman is the author of Learning By Simulating Evolution Using Corewars.
David G. Andersen has written a paper on evolving, The Garden: Evolving Warriors in Core Wars.
Assimilated evolution by Loren Roosendaal
Exploiting Co-Evolution and a Modified Island Model to Climb the Core War Hill by F. Corno, E. Sanchez and G. Squillero
On The Evolution of Corewar Warriors by F. Corno, E. Sanchez and G. Squillero
Evolving Assembly Programs: How Games Help Microprocessor Validation by F. Corno, E. Sanchez and G. Squillero