A. J. Turnbull et al. Shell Formation in NGC474Архивная копия от 20 октября 2017 на Wayback Machine. Galaxy Interactions at Low and High Redshift, Proceedings of IAU Symposium #186, held at Kyoto, Japan, 26-30 August, 1997. Edited by J. E. Barnes, and D. B. Sanders, 1999, p.191.
A. J. Turnbull et al. Shell Formation in NGC474Архивная копия от 20 октября 2017 на Wayback Machine. Galaxy Interactions at Low and High Redshift, Proceedings of IAU Symposium #186, held at Kyoto, Japan, 26-30 August, 1997. Edited by J. E. Barnes, and D. B. Sanders, 1999, p.191.