1. NLM Catalog: Journals referenced in the NCBI Databases [Internet]. Bethesda. U.S. National Library of Medicine. cited 2011 Jun 1. Available from: http://www.ncbi.nlm.nih.gov/nlmcatalog/journals
2. KoreaMed Synapse [Internet]. Seoul. Korean Association of Medical Journal Editors. cited 2011 Jun 1. Available from: http://synapse.koreamed.org/
3. BioMed Experts [Internet]. [place unknown]. Elsevier Inc. cited 2011 Jun 1. Available from: http://www.biomedexperts.com/
4. Scimago Journal & Country Ranking [Internet]. [place unknown]. Scimago Lab. c2007-2011. cited 2011 Jun 1. Available from: http://scopus.com/