The following publications contain information about William Slaper:

Article: "Fought with Reno in Sioux War: William C. Slaper of Los Angeles, Who Goes to Commemorate Custer's Last Stand, Describes Scenes of Memorable Engagement on Little Big Horn" by E. A. Brininstool • The Los Angeles Times • June 20, 1926 • Page 92.

Article: "Custer Battle Fought Again with Veterans of Fray on Sidelines"• The Pierce County (North Dakota) Tribune • July 1, 1926 • Page 1.

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.