Reddit reviews The Dao of Taijiquan: Way to Rejuvenation (Tai Chi)

Might not be popular advice, but this really helped me. I was reading a book called the dao of taijuquan and somewhere in the philosophy section, he says, even if you have a great master, ultimately it's you that's studying tai chi, not just the form, but the actual forces out there in the universe. So ultimately you have to teach yourself. It was pretty mind-blowing for me, and it got me out of the rut I was in of feeling like I needed to find some super high level master or I couldn't make any progress. No. Even if you do the opening move over and over, you're learning. Different people have different aptitude to extract knowledge directly from life itself, but once I realized that was possible life got very cool for me.

http://www.amazon.com/The-Dao-Taijiquan-Way-Rejuvenation/dp/0804813574

This goes into it a good bit, in addition to being a fantastic book on Tai chi in general.

Yang Jwing-Ming describes them in his book, Taijiquan Theory, beginning on page 146. Jou Tsung Hwa describes them in his book, The Dao of Taijiquan, starting on page 220. I know they are mentioned in the classics as well as books by Yang Chengfu, although I don't have any in front of me. Would you agree that these people understand taijiquan?

I heartily disagree with your statement that they are borrowed from other arts. These energies are the core of taiji. Without sticking, listening, and understanding; you do not have true taijiquan. Without neutralizing, seizing, and issuing; you do not have solid martial skill.

https://www.amazon.com/Dao-Taijiquan-Way-Rejuvenation-Tai/dp/0804813574
Master Jou's book is a good one.