Stapp & Bowman 1968, p. 48. Stapp, Catherine; Bowman, W. I. (1968). History Under Our Feet: the Story of Vermilion County, Illinois. Danville, Illinois: Interstate Printers and Publishers, Inc. ASINB002T9WTMC.
Edwards, Roger (March 5, 2015). "Enhanced F Scale for Tornado Damage". The Online Tornado FAQ (by Roger Edwards, SPC). Storm Prediction Center. Retrieved February 25, 2016.