Here are some of the abbreviations used in the text: NCBI: National Center for Biotechnology Information MEDLINE: MEDlars onLINE MEDlars: Medical Literature Analysis and Retrieval System NLM: The National Library of Medicine of the United States NIH: National Institutes of Health PubMed: Public MEDLINE – Publisher MEDLINE. MeSH database: Medical Subject Headings database [2] Hersh, W. Information Retrieval: A Health and Biomedical Perspective. Springer; 3rd edition (November 6, 2008) p. 124. [3] Fact Sheet MEDLINE: http://www.nlm.nih.gov/pubs/factsheets/medline.html (accessed November 7, 2009).