Lore A Rogers & Caleb W Scribner. “Lombard Steam Log Hauler”(PDF). American Society of Mechanical Engineers. 4 March 2009에 원본 문서(pdf)에서 보존된 문서. 6 January 2009에 확인함.
blogs.com
patentpending.blogs.com
“1907 Screw Drive Vehicle”. 《Patent Pending Blog – Patents and the History of Technology》. 2009년 1월 7일에 확인함.
espacenet.com
worldwide.espacenet.com
US patent 635501, J. A. Morath, "Agricultural Machine", issued 1899-05-18 An early patent for an auger driven farm tractor.
Lore A Rogers & Caleb W Scribner. “Lombard Steam Log Hauler”(PDF). American Society of Mechanical Engineers. 4 March 2009에 원본 문서(pdf)에서 보존된 문서. 6 January 2009에 확인함.