1. Kerr, F. J.: 1969, Australian. J. Phys. Astrophys. Suppl. 9, 1.
2. Mathewson, D. S., Healey, J. R., and Rome, J. M.: 1961, Australian. J. Phys. 15, 354.
3. Sandage, A.: 1961, The Hubble Atlas of Galaxies, Carnegie Institution of Washington, Washington.
4. Schmidt, M.: 1965, Stars and Stellar Systems 5, 528.
5. Schmidt-Kaler, T.: 1964, Trans.IAU 12B, 416.