Hilbert subspaces (= operator ranges); complementation (Aronszajn, de Branges, etc.), spaces of entire functions, isometric embeddings, subspaces of Pontryagin spaces of entire functions, Canonical models for contractions and nonselfadjoint linear operators, Spaces with indefinite inner product (Kreĭn spaces, Pontryagin spaces, etc.), Linear operators on spaces with an indefinite metric, Pontryagin space, Weyl coefficients of matrix chains, inverse spectral theorem for Nevanlinna functions, Pontryagin spaces, extensions of symmetric operators, Spaces of bounded analytic functions of one complex variable, Hilbert spaces with reproducing kernels (= (proper) functional Hilbert spaces, including de Branges-Rovnyak and other structured spaces), Hilbert spaces of continuous, differentiable or analytic functions