FASOM is hard to document as it is always changing.
Here is what I have:

• 2010 Model Documentation for the Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG)
  
  
• FASOMGHG Conceptual Structure, and Specification: 2005 Documentation
  
  
• A User's Guide To the Forest and Agricultural Sector Optimization Model ( FASOM)
  
  
• Forest and Agricultural Sector Optimization Model: Model Description
  
  
• An Analysis of the Impacts of Public Timber Harvest Policies on Private Forest Management in the United States
  
  
• Impacts of Incorporating Land Exchanges Between Forestry and Agriculture in Sector Models