Structural study of the ferroelectric instability in Sn2P2Se6R. Enjalbert, J. Galy, Y. Vysochanskii, A. Ouédraogo and P. Saint-GrégoireEur. Phys. J. B, 8 2 (1999) 169-177DOI: https://doi.org/10.1007/s100510050680