NED object is NGC 3198; Reference is  1987ApJS...65..485C

   Fig. 7. - Small contour maps, in order of increasing right ascension. The
 optical position of each galaxy is indicated by a cross. Contour levels are
 plotted at +- 2^n/2^, +- 2^(n+1)/2^, +- 2 ^(n+2)/2^,... mJy per restoring beam
 solid angle. The value of n for each galaxy is listed in Table 2.