1. 1. Sicard A . Extradural injection of medication by way of the sacroccygeal canal. C R Soc Biol (Paris) 1901; 53: 396.
2. 2. Cathelin F . A new route of spinal injection; A method of epidural injections by way of the sacral canal; application to man. C R Soc Biol (Paris) 1901; 53: 452.
3. 3. Sicard JA , Forestier J . Radiographic method of exploration of the external spaceusing Lipodol. Rev Neurol 1921; 28: 1264.
4. 4. Curbelo MM . Continuous peridural segmental anesthesia by means of a ureteral catheter. Anesth Analg 1949; 28: 1-13.
5. 5. Shal JL . Identification of the epidural space. Br J Hosp Med 1991; 46: 60-2.