Scattering matrices for microschemes.- 1. General expressions for the scattering matrix.- 2. Continuity condition.- References.- Holomorphic operators between Krein spaces and the number of squares of associated kernels.- 0. Introduction.- 1. Realizations of a class of Schur functions.- 2. Positive squares and injectivity.- 3. Application of the Potapov-Ginzburg transform.- References.- On reproducing kernel spaces, the Schur algorithm, and interpolation...