Common multiples of operator polynomials with analytic coefficients. M.A. Kaashoek, I. Goberg, F. Schagen (1978) Manuscripta mathematica
Commutative/noncommutative rank of linear matrices and subspaces of matrices of low rank. Fortin, Marc, Reutenauer, Christophe (2004) Séminaire Lotharingien de Combinatoire [electronic only]
Computation of the Smallest Positive Eigenvalue of a Quadratic ..-matrix. Rainer Garus, Tassilo Küpper (1990) Numerische Mathematik