The Southern Forest Products Association (SFPA) publishes the Permanent Wood Foundations Design and Construction Guide. Download the document here.
AWC's PWF Design Fabrication Installation (DFI) Manual and Technical Report #7, Permanent Wood Foundation System Basic Requirements (TR7) have both been discontinued and are out of print. ANSI / AF&PA PWF-2007 - Permanent Wood Foundation Design Specification replaces TR7 and has been adopted in the 2009/2012 International Residential Code and 2009/2012 International Building Code. This document primarily addresses structural design requirements. See the SFPA Permanent Wood Foundations Design and Construction Guide for construction details and tabulated data.