X-RAY STUDY OF PHASE TRANSITION INVOLVING ORDERED BIAXIAL PHASES G. ALBERTINI, B. DUBINI, S. MELONE, M. G. PONZI-BOSSI, F. RUSTICHELLI and G. TORQUATI J. Phys. Colloques, 40 C3 (1979) C3-384-C3-388 DOI: 10.1051/jphyscol:1979376