Quantification of L-tryptophan and L-kynurenine by liquid chromatography/electron capture negative ion chemical ionization mass spectrometry - Boni, R. L.; Simpson, J. T.; Naritsin, D. B.; Saito, K.; Markey, S. P. (Wiley-Blackwell, 1994)
http://dx.doi.org/10.1002/bms.1200230106
Keywords: V