Physics of mirrors, reversed field pinches and compact tori : proceedings of the course and workshop held at Villa Nonastero, Varenna, Italy, September 1-11, 1987 - Course and Workshop on Physics of Mirrors, Reversed Field Pinches and Compact Tori; International School of Plasma Physics; Ortolani, S.; Sindoni, E. (Elio); Società italiana di fisica (International school of plasma physics "Piero Caldirola", 1988)