1. Development of face gear technology for industrial and aerospace power transmission;Heath,2002
2. Application of face gear drives in helicopter transmissions;Litvin;J. Mech. Des.,1994
3. Hob for generating crown gears;Miller,1942
4. G. Basstein, A. Sijtstra, New Developments in Design, Manufacturing and Applications of Cylkro (Face) Gears, AGMA Fall Technical Paper 93FTM7, 1993.
5. Theoretical error of gear hobbing with spherical hob;Guo;J. Aeronaut. Dyn.,2009