I am one of Grahams senior students in London, I still meet up to practice with old students at The Place and refine the teachings of Graham taught, I have the earlier copies of the form moves and practice the relationships as Graham taught them. Over the years I have course have also developed my own understanding that correspond with my own interests.
As stated Stuart Olson’s book “T’ai Chi According to the I Ching” is a good reference but they may be derived from Grahams book and a knowledge of acupunture meridians. Some of us senior students normally practice at the place once per month or in regents park on sundays.
Hope that helps