http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TF9-4VG7MR2-8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=86fe231643abb85df081e9e883cc60c7
http://www.faqs.org/patents/app/20090105349
http://www.ncbi.nlm.nih.gov/pubmed/19900809
http://www.faqs.org/patents/app/20090105349
http://www.ncbi.nlm.nih.gov/pubmed/19900809