U.S. National Park Service, Technical Preservation Services
Internal Revenue Service, Rehabilitation Tax Credit Information
Internal Revenue Code Section 47 for Historic Rehabilitation Tax Credits
National Council for State Housing Agencies
Affordable Housing Investors Counsel
Internal Revenue Code Section 42 for Low Income Housing Tax Credits
U.S. Energy Information Administration, Renewable Energy Incentives Explained
DSIRE, Database of State Incentives for Renewables & Efficiency