1. Wijmenga, H. G., “Onderzoekingen over vitamin B12 en verwante factoren”, thesis, University of Utrecht (1951).
2. Ford, J. E., and Porter, J. W. G., Biochem. J., 51, v (1952).
3. Pfiffner, J. J., Calkins, D. J., Peterson, R. G., Bird, O. D., McGlohon, V., and Stipek, R. W., Amer. Chem. Soc., 120th meeting, abst. of papers, 22c (1951).
4. Lewis, V. J., Tappan, D. V., and Elvehjem, C. A., J. Biol. Chem., 194, 539 (1952).
5. Hausmann, K., Lancet, 257, 963 (1949).