1. Evidence based medicine: what it is and what it isn’t;Sackett;BMJ,1996
2. General Medical Council: Good Medical Practice; Providing Good Clinical Care; Paragraph 3b http://www.gmc-uk.org/guidance/good_medical_practice/good_clinical_care_index.asp
3. NHS Library Services & Wirral Health Informatics Service Internet Division 2011 http://www.libraryservices.nhs.uk/shall/
4. Fees for library service: they are not inevitable;Kranich;Library Journal,1980
5. User fees: aid or obstacle to access;Drake;Wilson Library Bulletin,1984