Low-temperature heat capacity of triangle antiferromagnetic molecular clusters K12[(VO)3(SbW9O33)2]·15H2O and K12[(VO)3(BiW9O33)2]·29H2O - Kohama, Yoshimitsu; Kawaji, Hitoshi; Atake, Tooru; Fukaya, Keisuke; Yamase, Toshihiro (Journal of Solid State Chemistry, 2009)