In the CIP rules the conventional order of @[email protected] established for the purpose of unambiguous designation of @[email protected] It is deduced by application of @[email protected], 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).