V.Fiocchi Nicolai, F.Bisconti and D.Mazzoleni, The Christian Catacombs of Rome: History, Decoration, Inscriptions (Regensburg, 1999), 20–22, 35, 151–153. A further good general introduction is J.Stevenson, The Catacombs: Rediscovered Monuments of Early Christianity (London, 1978).
