1. Labour is still painful after prepared childbirth training;Melzack;Can Med Assoc J,1981
2. Psychological correlates of childbirth pain;Davenport-Slack;Psychosom Med,1974
3. Pain relief during delivery;Bundsen;Acta Obstet Gynecol Scand,1982
4. Effectiveness of pain relief in labour: survey of 1000 mothers;Morgan;BMJ,1982
5. Severity of labour pain: influence of physical as well as psychologic variables;Melzack;Can Med Assoc J,1984