U. Frey, J. Claude, S. Crelier, and M.-A. Juillerat, “UV Degradation of Sesquiterpene Lactones in Chicory Extract: Kinetics and Identification of Reaction Products by HPLC-MS”, Chimia, vol. 56, no. 6, p. 292, Jun. 2002, doi: 10.2533/000942902777680450.