Analysis of information sources in references of the Wikipedia article "Subvariety" in English language version.
4.1. If a greater number of ranks of taxa is desired, [...a]n organism may thus be assigned to taxa of the following ranks (in descending sequence): [... genus, ... species, subspecies,] variety (varietas), subvariety (subvarietas), form (forma), and subform (subforma). ... 4.3. Further ranks may also be intercalated or added, provided that confusion or error is not thereby introduced.
