Vishnu Ji Ram, Arun Sethi, Mahendra Nath, Ramendra Pratap:The Chemistry of Heterocycles: Nomenclature and Chemistry of Three to Five Membered Heterocycles. Elsevier, 2019, ISBN 978-0-08-101191-1, S.110 (S. 110in der Google-Buchsuche).
Alan R. Katritzky, Christopher A. Ramsden, John A. Joule, Viktor V. Zhdankin:Handbook of Heterocyclic Chemistry. Elsevier, 2010, ISBN 978-0-08-095844-6, S.231 (S. 231in der Google-Buchsuche).