Ribonuclease inhibitor. Prepn from yeast ribonucleic acid: Cohn, Carter, J. Am. Chem. Soc. 72, 2606 (1950); Loring et al., J. Biol. Chem. 196, 807 (1952); by phosphorylation of N6,O3′,O5′-tribenzoylcytidine: Rammler, Khorana, J. Am. Chem. Soc. 84, 3112 (1962). Crystal structure and conformation of the trihydrate: Kartha et al., Science 179, 495 (1973). Reviews: See Cytidine.