Probability Winter School : Proceedings of the Fourth Winter School on Probability Held at Karpacz Poland January 1975 Stochatic systems of particles On Lévys Brownian Motion with several dimensional time Convergence of observables A limit theorem for truncated random variables Invariant Measures for piecewise monotonic transformations A limit theorem for triangular arrays of representations of canonical anti commutation relations Non commutative probability theory on von neumann algebras On unconditional bases and rademacher averages Topics in ergodic theory A more deterministic version of Harris Spitzers “Random constant velocity” model for infinite systems of particles Extreme point method in probability theory Stable symmetric probability laws in quantum mechanics Prediction theory in Banach spaces Geometry and martingales in Banach spaces A note on semipolar sets for processes with independent increments.