APA-referens (7:e uppl.)
ebrary, Inc, Gutzman, A. D., Muller, A., Pfledderer, D., & Gibbons, T. (2002). Buyers' guide to search engine optimization firms: Who should you hire? how much should you pay? (2nd ed.). MarketingSherpa.
Chicago-referens (17:e uppl.)
ebrary, Inc, Alexis D. Gutzman, Anthony Muller, Donna Pfledderer, och Tim Gibbons. Buyers' Guide to Search Engine Optimization Firms: Who Should You Hire? How Much Should You Pay? 2nd ed. Portsmouth, R.I.: MarketingSherpa, 2002.
MLA-referens (9:e uppl.)
ebrary, Inc, et al. Buyers' Guide to Search Engine Optimization Firms: Who Should You Hire? How Much Should You Pay? 2nd ed. MarketingSherpa, 2002.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.