H₂ mass vs. redshift for the z < 0.03 B2 radio galaxies (large empty symbols); for z < 0.03 3C radio galaxies (small empty symbols); for z < 0.0233 UGC galaxies (small filled symbols); and for the four (including Fornax A) z < 0.03 Southern radio galaxies observed so far (large filled symbols). Circles refer to detections and triangles to upper limits. Crosses indicate sources which display a double-horned CO line profile. Solid lines indicate the M_H2 3σ detection limit for σ () = 0.1, 0.2 and 0.4 mK respectively (assuming a 500 km s^-1 wide CO line, see Eq. (1)). The vertical dashed line at z = 0.0233 indicates the redshift limit to which all three Northern samples overlap.