The primary source(s) have been noted but not everyone can learn through the classic Roth-based associative memory system due to the odd redundancy they encourage. I've found this common with ADHD & Dyslexic individuals. This is also how & why my own
Easy Reading "method" came into being, evolving out of the Paul Hadley word code system (Easy Reading is available through Lybrary.com or mevproshop.com the Hadley book can be found at Hades Publishing in Canada or here
http://www.amazon.com/develop-mental-magic-Paul-Hadley/dp/B0007EL1SE )
Traditional systems encourage you to use an abstract memory anchor that in turn links to the thing you are trying to recollect e.g. you end up with two things you are attempting to remember. My system on the other hand, takes information most any 4th grade child would know and applies it with associations. In other words, if you know your alphabet and how to count from 1 to 1,000 (or more) you can use this technique at the mnemonic level, as a code system, and as part of your cold reading arsenal (based on Richard Webster formulas).
Also understand that there is a big difference in learning how to use this type of memory trigger and actual memorization.