Describes a compound that has a macroscopic composition such that its constituent nuclides
are present in the proportions occurring in nature.
PAC, 1981, 53, 1887
(Nomenclature of inorganic chemistry: II.1 - Isotopically modified compounds)
on page 1889
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