The series of five books written by Senior Grand Master Ed Parker about his Kenpo system have been republished, and are now selling via Amazon. Here is the link to the first one in the series, you can easily find the rest from that:

Ed Parker's Infinite Insights Into Kenpo: Mental Stimulation

This is great news for Kenpo practitioners, as these books have been out of print for a long, long time and became very difficult to acquire, in fact I only had the second one from five, but now I have the other four on order so will soon complete my collection :-)

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Updated 2021 : note that the above post was originally published in 2009, but is left here for archival purposes.