McKenna, M.C. & Bell, S.K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York.: i-xii, 1-631.
Nowak, R.M. 1991. Vol. I. Walker's Mammals of the World, Fifth Edition. The Johns Hopkins University Press, Baltimore and London: vii-xlv, 1-642, xlix-lxiii.
Corbet, G.B. & Hill, J.E. 1991. A World List of Mammalian Species, Third edition. Natural History Museum Publications & Oxford University Press, London and Oxford.: v-viii, 1-243.
McKenna, M.C. & Bell, S.K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York.: i-xii, 1-631.
DeBlase, A.F. 1982. Mammalia. In Parker, S.P., Synopsis and Classification of Living Organisms, vol. 2. McGraw-Hill, New York: 1015-1061.
Groves, C.P. 1993. Order Monotremata. In Wilson, D.E. & Reeder, D.M. (eds.) Mammal Species of the World, Second Edition. Smithsonian Institution Press, Washington and London.: 13.
Groves, C.P. 2005. Order Monotremata. In Wilson, D.E. & Reeder, D.M. (eds.) Mammal Species of the World, Third Edition. The Johns Hopkins University Press, Baltimore.: 1-2.
Griffiths, M. 1978. The Biology of the Monotremes. Academic Press, NY. 367 pp.