http://downloads.transportation.org/Audit-AccountingGuide.pdf - The Uniform Audit & Accounting Guide web site.  This guide was developed to bring consistency to the consultant audit process.  The purpose of this Guide is to provide Consultants, Independent audit firms and new auditors a basic understanding and a uniform reference guide for auditing and developing overhead rates.  See Chapter 9 which has information on "Schedule of Indirect Costs."

http://www.arnet.gov/far/ - This website gets you to the Federal Acquisition Regulations.  Select Part 31.2 "Contracts with Commercial Organizations" 48 CFR(Code of Federal Regulations) Part 31.