1. Brown, E. V. and Moser, R. J. (1971). Mass spectra of some 2-,3-, and 4-pyridine carboxylic acids. Further evidence of a N-H interaction from loss of carbon dioxide. J. Heterocyclic Chem., 8, 189–192.
2. Cavins, J. F. and Friedman, M. (1970). Preparation and evaluation of S-β-(4-pyridylethyl)-L-cysteine as an internal standard for amino acid analyses. Anal. Biochem., 35, 489–493.
3. Elliott, W. H. and Waller, G. R. (1972). Vitamins and cofactors. In “Biochemical Applications of Mass Spectrometry,” G. R Waller, Ed., Wiley-Interscience, New York, New York, Chapter 18.
4. Friedman, M. (1973). “The Chemistry and Biochemistry of the Sulfhydryl Group in Amino Acids, Peptides, and Proteins,” Pergamon Press, Oxford, England and Elmsford, New York, 485 + viii p.
5. Friedman, M. and Noma, A. T. (1970). Cystine content of wool. Textile Res. J., 40, 1073–1078.