written published sources

The five main written published sources in the last nine years are in the order I read them over about that time span are:

1 Tai Chi by Paul Tucker, Lorenz Books, ISBN 1-85967-503-4
2 Principles of Tai Chi by Paul Brecher, Thorsons, ISBN 0-7225-3474-4
3 T'ai-Chi, The "Supreme Ultimate" Exercise for Health, Sport, and Self-Defense by Cheng Man-ch'ing and Robert W. Smith, Tuttle & Co., ISBN 0-8048-0560-1
4 The Tai Chi Book by Robert Chuckrow, YMAA Publication Center, ISBN 1-88696-64-7
5 T'ai Chi Ch'uan Ta Wen by Chen Wei-Ming, North Atlantic Books, ISBN 0-938190-67-9

They all helped me at the stage I first read them, the last three in particular are still referred to regularly.