?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adissertation&rft.au=Chandrasekera%2C+Dhammitha+Himali&rft.aufirst=Dhammitha+Himali&rft.aulast=Chandrasekera&rft.date=2004&rft.tpages=210&rft.title=Analytical+investigations+of+St.+John's+wort+herbal+preparations.&rft.inst=University+College+London&rft.degree=Doctoral