Domonoske, Arthur Boquer; Finch, Volney Cecil (1936). Aircraft Engines: Theory, Analysis, Design and Operation (Engineering textbook). J. Wiley & Sons. s. 7. Besøkt 25. april 2014. «The W, or broad arrow engine, has three rows of cylinders of which the central row is vertical with the other two rows forming equal angles with the vertical.»
