The Rhodes-Wohlfarth parameter as assessment of the displacive degree in ferroelectrics: The case of the φ4 modelJ. M. Perez-Mato, I. Etxebarria, S. Radescu and S. IvantchevEur. Phys. J. B, 12 3 (1999) 331-334DOI: https://doi.org/10.1007/s100510051012