A Practical Guide to Qabalistic Symbolism  by Gareth Knight

Chapter IX  (pgs. 101-112)

The Mystical Qabala  by Dion Fortune

pgs. 329-341

Magic of the Qabalah  by Kala Trobe

pgs. 219-223

Other Sources:

A Garden of Pomegranates,  Israel Regardie 

The Middle Pillar,  Israel Regardie

The Elements of Qabalah,  Will Parfitt

Magical States of Consciousness,  Melita Denning and Osbourne Phillips

Tarot and the Tree,  Isabel Kliegman

The Chicken Qabalah,  Lon Milo Duquette

The Miracle Tree,  R.J. Stewart

The Ladder of Lights,  William Gray