^ ab Wells, A. F. (1984). Structural Inorganic Chemistry, 5th Ed., Oxford Science Publications. (ISBN 0-19-855370-6).
^Conroy, L. E.; Ben-Dor, L. (1995). "Molybdenum(IV) Oxide and Tungsten(IV) Oxides Single-Crystals." Inorganic Syntheses, Vol. 30, pp. 105-107. (ISBN 0-471-30508-1).