nonselectively labelled

https://doi.org/10.1351/goldbook.N04202
An @[email protected] compound is designated as nonselectively labelled when the position(s) and the number of the @[email protected] @[email protected] are both undefined.
Sources:
Blue Book, p. 517 [Terms] [Book]
PAC, 1981, 53, 1887. (Nomenclature of inorganic chemistry: II.1 - Isotopically modified compounds) on page 1896 [Terms] [Paper]