Caermon, A.G.W., 1962: Star formation in elliptical galaxies and intense radio sources. Nature, 194, 963-964, doi:10.1038/194963a0.
G.R. Burbidge has recently reviewed the problem of the energy sources required to give the non-thermal radio emission from intense extragalactic sources. The intrinsically strongest sources appear to be mostly associated with giant elliptical galaxies, and to be radiating at power-levels up to 107 times that of our own Galaxy. Burbidge argues convincingly that the high-energy particles responsible for the radio emission must be accelerated in supernova explosions. A typical strong radio source would require the explosion of 107 or 108 supernovæ in a period of 107 or 108 years. This is a considerably greater supernova-rate than normally occurs in a galaxy.