Bazoti FN, Gikas E, Puel C, Coxam V, Tsarbopoulos A. Development of a Sensitive and Specific Solid Phase Extraction? Gas Chromatography? Tandem Mass Spectrometry Method for the Determination of Elenolic Acid, Hydroxytyrosol, and Tyrosol in Rat Urine. Journal of agricultural and food chemistry. 2005;53(16):6213-6221.