Twins Network
http://twinsnetwork.com

Spence Chapin Services
www.spence-chapin.org

The Twins Foundation
www.twinsfoundation.com

Double Up Books
www.doubleupbooks.com

The Adoption History Project
http://darkwing.uoregon.edu/~adoption

International Soundex Reunion Registry
www.isrr.net

Evan B. Donaldson Adoption Institute
www.adoptioninstitute.org