NED object is NGC 3521; Reference is 1987A&AS...70..517H

   Figure 2. - Contour maps of sources not coincident with the nuclei and which
 are background sources (except N1087 ?). See table II for the map parameters
 and the notes for comments on these sources. NGC 3521 Contours plotted (mJy
 per beam) -1, -0.5, 0.5, 1..., 10 steps of 1 HPBW (arcsec) 2.5 r.m.s. noise
 (mJy per beam) 0.22.