Du Bose, John Witherspoon. General Joseph Wheeler and the Army of the Tennessee. Neale Publishing Company, 209. o. (1912. december 1.). ISBN 9780722280065 „As far as the eye reached, white-top wagons, drawn each by six handsomely harnessed mules, trailed along the narrow road. As the way pushed up the mountain, far away, the white-tops slowly ascended with it.”
Harper, Douglas. ambulance, The Online Etymological Dictionary (2001–2022) „In late 19c. U.S. the same word was used dialectally to mean 'prairie wagon.'”
