Name Info Provider Link
free resource Medknow Publications and Media Pvt Ltd http://www.joacp.org/article.asp?issn=0970-9185;year=2011;volume=27;issue=3;spage=393;epage=394;aulast=Williams
subscription/membership/fee required Ovid Technologies, Inc. http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21897517.ui
free resource PubMed Central https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21897517/
free resource Europe PubMed Central https://europepmc.org/abstract/MED/21897517