5Litivin F L, et al. Design and geometry of face-gear drive[J]. Transaction of the ASME, Journal of Mechanical Design, 1992,114:642 -647
6Iitivin F L, et al. Application of face-gear drives in helicopter transmissions[J]. Transactions of the ASME, Journal of Mechanical Design, 1994,116:672 -676
7Handschuh R F, et al. Experimental Testing of Prototype Face-gears for Helicopter Transmissions[R ]. NASA TM-105434,1992
