Positron annihilation lifetime study of pure and Na(acac) treated polyvinylalcohol A.M.A. EL-SAYED, E.E. ABDEL-HADY, M. MOHSEN et A. SAWABY J. Phys. IV France, 03 C4 (1993) C4-271-C4-273 DOI: 10.1051/jp4:1993442