Taxon - Odkazy a literatura
Paleobiology Database [7634]
Paleobiology Database [https://paleobiodb.org/] [jako Circotheca Syssoiev, 1958]
Datum citace: 30. leden 2016
The Interim Register of Marine and Nonmarine Genera [1440773]
Rees, T. (compiler): The Interim Register of Marine and Nonmarine Genera [https://www.irmng.org] [jako Circotheca Sysoev, 1958]
Datum citace: 30. listopad 2019
Marek L. (1989): The hyoliths of the Králův Dvůr formation (Bohemian Ordovician), Sbor. geol. věd, Paleontologie 30, 37-59 [jako Circotheca Syssoiev, 1958]