Factorizations into Normal Matrices in Indefinite Inner Product Spaces
  We show that any nonsingular (real or complex) square matrix can be factorized into a product of at most three normal matrices, one of which is unitary, another selfadjoint with eigenvalues in the open right half-plane, and the third one is normal involutory with a neutral negative eigenspace (we call the latter matrices normal neutral involutory). Here the words normal, unitary, selfadjoint and neutral are understood with respect to an indefinite inner product. 
Xuefang Sui, Paolo Gondolo (University of Utah)
math.RA math.NA