1. “Antiferroelectric phase transition in Sr9In(PO4)7”. Stefanovich SY, Belik AA, Azuma M, Takano M, Baryshnikova OV, Morozov VA, Lazoryak BI, Lebedev OI, Van Tendeloo G, Physical review : B : condensed matter and materials physics 70, 172103 (2004).   http://doi.org/10.1103/PhysRevB.70.172103