1. Der negative vorschlag bei lumbalpunktion;Janzen;Deutsche Zeitschrift für Nervenheilkunde,1926
2. Negative pressure in the epidural space;Heldt;American Journal of the Medical Sciences,1928
3. Note sur la pression épidurale négative;Bonniot;Bulletin de la Société de Chirurgie de Paris,1934
4. The identification of the epidural space;Dawkins;Anaesthesia,1963
5. Epidural pressure and its relation to spread of anesthetic solutions in epidural space;Usubiaga;Anesthesia and Analgesia; Current Researches,1967