Huber, H. & Stetter, K.O. 2001. Order I. Methanopyrales ord. nov. In D.R. Boone & R.W. Castenholz (eds.), Vol. 1: The Archaea and the Deeply Branching and Phototrophic Bacteria. In G.M. Garrity (ed.), Bergey's Manual of Systematic Bacteriology, 2nd ed., Springer-Verlag, New York.: 353-355.