A new class of unitarizable highest weight representations of infinite dimensional Lie algebras -- Formal integrability of systems of partial differential equations -- Quantum integrability and classical integrability -- Bäcklund transformations for nonlinear field equations -- Spectral transform approach to Bäcklund transformations -- Gauge coupling of non-linear ?-model and a generalized Mazur identity -- Magnetic monopoles -- Multimonopoles and the Riemann-Hilbert problem -- Classical solutions of Yang-Mills fields (selected topics) -- Stationary solutions of the Einstein-Maxwell equations -- Non linear sigma models: A geometrical approach in quantum field theory -- An approach towards the quantization of the relativistic closed string based upon symmetries -- Yang-Baxter charge algebras in integrable classical and quantum field theorie -- The quantum Toda chain -- On soluble cases of staggered ice-rule on a square lattice -- Fields on a random lattice II random surfaces : A search for a discrete model -- Products of random matrices and one dimensional disordered systems -- Exact disorder solutions -- The Coulomb gas systems : Some rigorous results -- Instanton contribution to the CP1-model with periodic boundary conditions -- Stochastic quantization and gravity -- Feynman's checkerboard and other games.