1. J.K. Baksalary, Algebraic characterizations and statistical implications of the commutativity of orthogonal projectors, in: T. Pukkila, S. Puntanen (Eds.), Proceedings of the Second International Tampere Conference in Statistics, University of Tampere, Tampere, Finland, 1987, pp. 113–142
2. On the product of oblique projectors;Groß;Linear and Multilinear Algebra,1998
3. Quadratic Forms in Random Variables: Theory and Applications;Mathai,1992
4. Generalized Inverse of Matrices and Its Applications;Rao,1971
5. On oblique projectors;Takane;Linear Algebra Appl.,1999