Observations of radio sources formerly considered as possible supernova remnants

A number of radio sources which have at some time been regarded as possible SNRs, or parts of SNRs, have been investigated. Our measurements of the spectrum and, in some instances, the detection of hydrogen recombination line emission, show that most of these sources are probably not SNRs. In each of two cases a proposed large-diameter SNR appears to be predominantly thermal but contains a source which may be an SNR of much smaller size than originally suggested. (author)