Another opportunity to get...Jeff Kreiter's "45 RPM Vocal Group Record Guide"--A Reference & Price Guide to Vocal Group Harmony Records (1949-2003). This book totally documents the harmony sound with listings of over 20,000 records of vocal group harmony by over 3,000 R&B, Doo-Wop, Girl, Transitional-Soul and and Pop Groups--Over 541 pages. This book is considered the "Bible" of doo-wop collectors.
http://www.ebay.com/itm/45-RPM-Vocal-Group-Record-Guide-8th-Edition-by-Jeff-Kreiter-DOO-WOP-/131544879858?pt=LH_DefaultDomain_0&hash=item1ea0af92f2