METAL-NON METAL TRANSITIONS IN TRANSITION METAL COMPOUNDS.THE ELECTRONIC PHASE TRANSITIONS IN FeS AND NiS J.M.D. COEY, H. ROUX-BUISSON et R. BRUSETTI J. Phys. Colloques, 37 C4 (1976) C4-1-C4-10 DOI: 10.1051/jphyscol:1976401