A specifically labelled
compound is referred to as mixed labelled when the isotopically substituted
compound has more than one kind of modified atom e.g.
PAC, 1981, 53, 1887
(Nomenclature of inorganic chemistry: II.1 - Isotopically modified compounds)
on page 1893
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook