Middleton, William D.; Smerk, George; Diehl, Roberta L., eds. (2007). "Poling Yards". Encyclopedia of North American Railroads. Bloomington and Indianapolis: Indiana University Press. p. 281. ISBN978-0-253-34916-3 – via Google Books.
Droege, John Albert (1906). "Chapter X: Pole Switching". Yards and Terminals and Their Operation. New York: The Railroad Gazette. pp. 97–103 – via Google Books.