Completing the spectrum of 2-chromatic S(2,4,v)

We construct 2-chromatic S(2,4,v) for v=37,40, and 73. This completes the proof of the existence of 2-chromatic Steiner systems S(2,4,v) [equivalently, of Steiner systems S(2,4,v) with a blocking set] for all v≡1 or 4 (mod 12).