R. Katiyar, Hans Schmid, J. F. Scott, Paul Tissot, J. Robertson, G. Catalan, R. Palai, S. A. T. Redfern, S. J. Clark,
β phase and γ-β metal-insulator transition in multiferroic BiFeO3 Physical Review B. ,vol. 77, pp. 014110- ,(2008) ,
10.1103/PHYSREVB.77.014110