MAHTESSIAN, Abraham. Groups of galaxies. III. Some empirical characteristics. Astrophysics. Juillet 1998, s. 308–321. Dostupné online. doi:10.1007/BF03036100.
MAHTESSIAN, Abraham. Groups of galaxies. III. Some empirical characteristics. Astrophysics. Juillet 1998, s. 308–321. Dostupné online. doi:10.1007/BF03036100.