SAFE SCUBA, by Bill Hogan, was an early to mid 70's textbook used by NASDS. I lost my copy years ago, but hoping somebody here has one and can look up a quote about the SOS Decompression Meter. In the edition that I had I recall the text saying something to the effect that the dive tables were too complicated for repetitive diving, and you should purchase the meter instead. The book seemed like more of a Scubapro sales promotion than a textbook.
NASDS had a real hard-sell line to help the stores sell Scubapro gear. We were NAUI, but had good friends with NASDS shop, and gave them a hard time about it standing for "National Association of Screw the Diver Stores".
If you have a copy and can find that info on the SOS, please post as much of the information as you deem interesting... especially the part that I mentioned above.