1. Sz-Nagy, B. (1953) Sur les contractions de l’espace Hilbert. Acta Scientiarum Mathematicarum, 15, 87-92.
2. Sz-Nagy, B. and Foias, C. (1970) Harmonic Analysis of Operators on Hilbert Space. Springer, Berlin.
3. The Von Neumann Inequality for Polynomials of Degree Greater Than Two
4. Lubin, A. (1978) Research Notes on von Neumann’s Inequality. International Journal of Mathematics and Mathematical Sciences, 1, 133-136.
5. Brehmer, S. (1961) Uber vertauschbare Kontractionen des Hilbertschen Raumes. Acta Scientiarum Mathematicarum, 22, 106-111.