SPECIFIC HEAT OF THE QUASI 2D-XY HELIMAGNETS BaCo2(AsO4)2 AND BaCo2 (PO4)2 L.P. Regnault, J. Rossat-Mignod, J. Villain et A. de Combarieu J. Phys. Colloques, 39 C6 (1978) C6-759-C6-761 DOI: 10.1051/jphyscol:19786339