Validation of a two-dimensional gas chromatography mass spectrometry method for the simultaneous quantification of cannabidiol, Δ9-tetrahydrocannabinol (THC), 11-hydroxy-THC, and 11-nor-9-carboxy-THC in plasma - Karschner, E L; Barnes, A J; Lowe, R H; Scheidweiler, K B; Huestis, M A (Anal Bioanal Chem, 2010)