These are some related sites of interest:
J. G Bennett Foundation Online ".... where you will find information and resource material concerning John G. Bennett; his life and work" This site has a large selection of books, including "Elementary Systematics", or you can order it on Amazon through this link.
The DuVersity The program of the DuVersity includes both research and education. It sets up dialogue groups, gives courses in corresponding and affiliated methods and organizes seminar-dialogues on wide-ranging themes. It furthers research into methods of thinking, inter-disciplinary studies and cross-cultural communication.
The Center for Self-Organizing Leadership - A holistic approach to organizational transformation. This is Richard Knowles site where he describes using the Process Enneagram©, the consulting services that he offers, and the two books that he has written.
Bennett Books Bennett Books has for many years played a significant role in keeping most of J. G. Bennett's major works in print. They also carry a significant number of other 4th Way books, recordings and music.
Wikipedia This links to the Wikipedia article on Systematics (which currently could use some additional material).
SYSTEMATICS A NEW TECHNIQUE IN THINKING This is a short but comprehensive article on Systematics from the monad to the duodecad - Anthony Blake.