8457 C. Goffman/G. Pedrick: First course in functional analysis.
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8455 Stefan Kaczmarz/Hugo Steinhaus: Theorie der Orthogonalreihen.
Chelsea 1951.

Barry Simon: OPUC on one foot. Bull. AMS ... (2005), ...
An introduction to orthogonal polynomials on the unit circle.

17896 Francesco Tricomi: Vorlesungen über Orthogonalreihen. Springer 1955, 260p.