CHALCOGENIDE AND OXYCHALCOGENIDE GLASSES : EVOLUTION OF THE GALLIUM SURROUNDING WITH THE OXYGEN CONTENT S. BENAZETH, M.H. TUILIER, H. DEXPERT, M. GUITTARD et D. CARRE J. Phys. Colloques, 47 C8 (1986) C8-419-C8-422 DOI: 10.1051/jphyscol:1986884