1. Harada O, Shibata Y, Yamaguchi K. Power output apparatus and method of controlling the same: U.S. Patent 6,067,801. 30 May 2000.
2. Benford HL, Leising MB. The lever analogy: a new tool in transmission analysis. SAE Technical Paper; 1981.
3. Koide T, Matsui H, Nada M. Hybrid vehicle drive system having two motor/generator units and engine starting means: U.S. Patent 5934395. 1999-8-10.
4. Hata H, Matsui H, Ibaraki R. Power output device, hybrid vehicle and method of controlling them. China Patent CN1336879. 20 Feb 2002.
5. Oba H, Yamanaka A, Katsuta H, Kamichi K. Development of a hybrid powertrain system using CVT in a minivan. SAE Technical Paper. 2002-01-0991.