1. 1) Takeda, Y., et al., SAE Transactions, Vol.105, J. of Fuels & Lubricants, Paper No.961163, (1996), pp.938-947.
2. 2) Yanagihara, H., et al., 17th Int. Vienna Motor Symposium, (1996), pp.303-314.
3. 3) Nakagome, K.,et al., SAE Paper No.970898, (1997).
4. 4) Suzuki, H., et al., SAE Paper No.980509, (1998).