«NASA/IPAC Extragalactic Database». Results for NGC 1023. Jet Propulsion Laboratory, California Institute of Technology. [Consulta: 30 març 2013].
«NASA/IPAC Extragalactic Database». Results for Perseus+CLUSTER. Jet Propulsion Laboratory, California Institute of Technology. [Consulta: 19 maig 2013].
Kukarkin, B. V.; Kholopov, P. N.; Pskovsky, Y. P.; Efremov, Y. N.; Kukarkina, N. P.; 1 General Catalogue of Variable Stars, 1971. Bibcode: 1971GCVS3.C......0K.