Soltis A., Mednis E., Hartston W., Peters J. Understanding the Open Games (Except Ruy Lopez)

London: RHM Press, 1980. — 142 p. — ISBN: 9780890580509.
This book explains the logical basis of every chess move, idea, and variation in every important opening system, showing how each move plays its necessary part in the system's logical structure. The discussion, sometimes extending as far as the endgame, is presented in plain English, avoiding obscure move-analysis and imprecise symbols