Withers Publishing
Book

Norfolk Southern Locomotive Directory 2009-2010
Walthers Part # 95-106, p. 973 Walthers 2011 HO Scale Reference
A scale, $26.95, currently in stock at Walthers

 
A unit-by-unit listing with 150-plus b&w photographs including rebuilt slugs, GP40-2s, ES44ACs, and new GenSet units.