1. J. L. Wray, in “Molecular and Genetic Aspects of Nitrate Assimilation,” ed. by J. L. Wray and J. R. Kinghorn, Oxford Science Publications, New York, 1989, pp. 244–245.
2. O. Ouchterlony, in “Handbook of Experimental Immunology,” ed. by D. M. Weir, Blackwell Scientific, Oxford, Edinburgh, 1967, p. 676.