Displacive-order-disorder crossover at the ferroelectric-paraelectric phase transitions of BaTiO3 and LiTaO3 K.A. Müller, Y. Luspin, J.L. Servoin et F. Gervais J. Physique Lett., 43 15 (1982) 537-542 DOI: 10.1051/jphyslet:019820043015053700