In the CIP rules the conventional order of ligands established for the purpose of unambiguous designation of stereoisomers. It is deduced by application of sequence rules, the authoritative statement of which appears in R.S. Cahn, C.K. Ingold and V. Prelog, Angew. Chem.78, 413-447 (1966), Angew. Chem. Internat. Ed. Eng. 5, 385-415, 511 (1966); and V. Prelog and G. Helmchen, Angew. Chem. 94, 614-631 (1982), Angew. Chem. Internat. Ed. Eng. 21, 567-583 (1982).