From wikipedia (http://en.wikipedia.org/wiki/Warhammer_Fantasy_Battle):
The Third Edition of the game was published as a single hardback book in 1987. It had the most in-depth and complex movement and manoeuvre system of any edition. Other changes included a variety of new specialist troop types, rules for war machines and a more finely tuned system of representing heroes and wizards. It kept the same magic system and open-ended army design system as the first two editions. However, by this stage the use of army lists was very much encouraged. Army lists for this edition were published in a separate book called Warhammer Armies in 1988, until then use of the 2nd Editions Ravening Hordes list was encouraged.