T. Ishiyama, T. Iijima, T. Sugawara, K. Shibuya, H. Sato, Y. Terada, M. Ichikawa, D. I. Sessler, T. Matsukawa,
The use of patient-controlled epidural fentanyl in elderly patients* Anaesthesia. ,vol. 62, pp. 1246- 1250 ,(2007) ,
10.1111/J.1365-2044.2007.05256.X