1. Gottesman, S. T., thesis, Univ. Manchester (1967).
2. de Jager, G., thesis, Univ. Manchester (1967).
3. de Vaucouleurs, G., and A., Reference Catalogue of Bright Galaxies (Univ. Texas Press, 1964).
4. Roberts, M. S., Astrophys. J., 144, 639 (1966).
5. Arp, H., IAU Symp. No. 20, The Galaxy and the Magellanic Clouds (edit. by Kerr, F. J., and Rodgers, A. W.), 219 (1964).