1. Ding L, Huang X, Yang J, Bian X, Zhang Z, Liu G: Determination of glycyrrhetic acid in human plasma by LC-ESI-MS. J Pharm Biomed Anal. 2006 Feb 24;40(3):758-62. doi: 10.1016/j.jpba.2005.10.047. Epub 2005 Dec 7. [PubMed:16337769 ]