Fremmerlid, M. (2007). What became of sigvald, anyway?: Was he The mad trapper of rat river?. Amazon. https://www.amazon.com/Became-Sigvald-Anyway-Trapper-River/dp/0978427009
Hunt for the mad trapper II. Myth Merchant Films. (n.d.). https://mythmerchantfilms.com/library/hunt-for-the-mad-trapper-ii/
Myth Merchant Films. (2021, July 30). Scientists narrow search for mysterious mad trapper to Sweden. GlobeNewswire News Room. https://www.globenewswire.com/news-release/2021/07/30/2272445/0/en/Scientists-Narrow-Search-For-Mysterious-Mad-Trapper-To-Sweden.html
Smith, B. (2014, May 23). The Mad Trapper: Unearthing a Mystery. Discovery. https://www.discovery.com/
Unidentified male. 3362UMYT. (n.d.). https://www.doenetwork.org/cases/3362umyt.html
Wikimedia Foundation. (2023, July 5). Albert Johnson (criminal). Wikipedia. https://en.wikipedia.org/wiki/Albert_Johnson_(criminal)