1. Havard, M., and A. Wanders: Power Sources – Animals. In: CIGR Handbook of Agricultural Engineering, Vol. III, 22–41. St Joseph MI: ASAE 1999.
2. Cerovic, V, Z. Mileusnic, and D.V. Petrovic: Theoretical limits of the angular stability range of the tractor moving over inclined terrain. 43. Symposium “Actual Tasks on Agricultural Engineering” Feb. 24–27. 2015 Opatija. Proceedings 111–121.
3. Ipek, I.: Über die Kräfte und Momente an einem Luftreifen und ihrem Einfluss auf das Verhalten luftbereifter Fahrzeuge am Hang (Mechanics of air inflated tires and their influence on vehicles on slopes). Ph.D. thesis TH Braunschweig 1959.
4. Ogorkiewicz, R.M.: Off-the-road vehicles. Recognizing M.G. Bekker who received an Honorary Doctor Degree from Technical University Munich in 1963. J. of Terramechanics 1 (1964) No. 1, 118–123.
5. Bekker, M.G.: Theory of Land Locomotion. Ann Arbor, MI: University of Michigan Press. 1956.