SPECIFIC HEAT OF THE TWO-DIMENSIONAL SPIN-1/2 HEISENBERG FERROMAGNET BLOEMBERGEN (P.), K.G. TAN, F.H.J. LEFEVRE et A.H.M. BLEYENDAAL J. Phys. Colloques, 32 C1 (1971) C1-878-C1-879 DOI: 10.1051/jphyscol:19711310