1. 1) Twycross R. G., Fairfield S., Pain, 14, 303-310 (1982).
2. 2) Bonica J. J., “The Management of Pain, Cancer pain: Current status and future needs,” 2nd ed., Lea & Febiger, Philadelphia, 1990, pp. 400-445.
3. 3) Kane R. L., Wales J., Bernstain L., Leibowitz A., Kaplan S., Lancet, 21, 890-894 (1984).
4. 4) Foley K. M., N. Engl. J. Med., 313, 84-95 (1985).
5. 5) Tsuneto S., Ikenaga M., Hosoya J., The Japanese Journal of Hospice and Palliative Care, 6, 482-490 (1996).