A Search for Sub-millisecond Pulsations in Unidentified FIRST and NVSS   Radio Sources
  We have searched 92 unidentified sources from the FIRST and NVSS 1400 MHz radio survey catalogs for radio pulsations at 610 MHz. The selected radio sources are bright, have no identification with extragalactic objects, are point-like and are more than 5% linearly polarized. Our search was sensitive to sub-millisecond pulsations from pulsars with dispersion measures (DMs) less than 500 pc cm-3 in the absence of scattering. We have detected no pulsations from these sources and consider possible effects which might prevent detection. We conclude that as a population, these sources are unlikely to be pulsars. 
Fronefield Crawford (MIT), Victoria M. Kaspi (MIT), Jon F. Bell (ATNF)