For those wondering what Bryan is talking about, see this link:
http://www.geocities.com/TimesSquare/9329/struct.htm
Considering the other two principles are Perrin and Petersen, we can assume that this rule is indeed, attributed to Greg. As are a lot of things that are now 'standard' in the RPG industry (story seeds, frex)
My Google-fu is strong today.
Jeff
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