1. Wildhaber E., Helical gearing, patent US 1601750, 1926
2. Novikov M.L., Gear transmissions and cam mechanisms with a point meshing system, patent SU109113, 1956 (in Russian)
3. Helical Gears With Circular Arc Teeth: Simulation of Conditions of Meshing and Bearing Contact
4. Kudrjavcev V.N., Derzhavec J.A., Gluharev E.G., Design and calculation of reduction gears, Mashinostroenie, Leningrad, 1971 (in Russian)