In 1969 a theoretical Physics Group was created at the Physics Department of the Federal Institute of Technology of Lausanne. In those days it was decided to initiate research on selected topics of Statistical Physics, in particular on the statistical mechanics of Lattice Systems. C. Gruber, a Ph. D. from Princeton University, who had joined the Group that same year, conducted this part of the research programme. In 1971 two graduate students from E.T.H. Zurich, A. Hintermann and D. Merlini started to work on their Ph.D. thesis with C. Gruber as thesis advisor.