1. Lecture Notes;T Ando,1979
2. T. Ja. Azizov and E. I. Iohvidov. The development of some of V. P. Potapov’s ideas in the geometric theory of operators in spaces with indefinite metric. in: Matrix and Operator Valued Functions OT 72, eds. I. Gohberg and L.A. Sakhnovich, Birkhäuser, Basel, 1994, 17–27.
3. A. Berman, and R. J. Plemmons, Nonnegative Matrices in the Mathematical Sciences, Academic Press, New York, 1979; also: SIAM, Philadelphia, 1994.
4. J. Bognár. Indefinite Inner Product Spaces, Springer, Berlin, 1974.
5. Yu. Bolshakov, C. V. M. van der Mee, A. C. M. Ran, B. Reichstein, L. Rodman. Polar decompositions in finite dimensional indefinite scalar product spaces: General theory, Linear Algebra and its Applications, submitted for publication.