The following publication contains information about William Slaper:
Article: "'An agreeable sort when sober:' The Myth of Michael Madden" by Douglas Scott • Pvt. Michael Madden's loss of his leg at the Little Bighorn is one of the more familiar tales associated with the June 25, 1876, action. But what is fact and what is fiction in Madden's story" Douglas Scott provides that insight. • Greasy Grass, Journal of the Custer Battlefield Historical & Museum Association, Vol. 25, May 2009.