Studies on polymeric insulators for transmission systems under natural aging conditions - Ramírez, J; Sabino, M; Da Silva, E; Rodríguez, J; Martínez, M; Bermúdez, J; Ren, J; Ferraz, A (1998 Annual Report Conference On Electrical Insulation And Dielectric Phenomena, Vols 1 And 2, 1998)