POINCARE POLYNOMIALS AND LEVEL RANK DUALITIES IN THE N=2 COSET CONSTRUCTION

We review the coset construction of conformal field theories; the emph asis is on the construction of the Hilbert spaces for these models, es pecially if fixed points occur. This is applied to the N = 2 superconf ormal cosets constructed by Kazama and Suzuki. To calculate heterotic string spectra we reformulate the Gepner construction in terms of simp le currents and introduce the so-called extended Poincare polynomial. We finally comment on the various equivalences arising between models of this class, which can be expressed as level rank dualities.