Normal forms, inner products and Maslov indices of general multimode   squeezings
  In this paper we present a pure algebraic construction of the normal factorization of multimode squeezed states and calculate their inner products. This procedure allows one to orthonormalize bases generated by squeezed states. We calculate several correct representations of the normalizing constant for the normal factorization, discuss an analogue of the Maslov index for squeezed states, and show that the Jordan decomposition is a useful mathematical tool for problems with degenerate Hamiltonians. As an application of this theory we consider a non-trivial class of squeezing problems which are solvable in any dimension. 
A. M. Chebotarev and T. V. Tlyachev
quant-ph