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.
Using Core War to Simulate Evolution by Terry Newton documents some experiments with RedMixer, followed by a detailed analysis of the evolver's source code.
Evolving Core Warriors by Dave Hillis uses ga_war.c as a starting point and experiments with different techniques to try to achieve better performance.
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.
An Evolutionary Approach Generates Human Competitive Corewar Programs by Barkley Vowk, Alexander (Sasha) Wait and Christian Schmidt
Assimilated evolution: defeating new strategies by exploiting their predecessors was submitted to the 19th Belgium-Netherlands Artificial Intelligence Conference 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 [broken link]
On The Evolution of Corewar Warriors by F. Corno, E. Sanchez and G. Squillero [broken link]
Evolving Assembly Programs: How Games Help Microprocessor Validation by F. Corno, E. Sanchez and G. Squillero [broken link]