1. L.V. Ahlfors, Complex analysis, 3rd ed., McGraw-Hill, New York, 1978.
2. N.I. Akhiezer and I.M. Glazman, Theory of linear operators in Hilbert space, English transl. by E.R. Dawson based on 3rd Russian ed., Pitman, London, 1981.
3. D. Amir, Characterizations of inner product spaces, Birkhäuser, Basel, 1986.
4. M.F. Atiyah and I.G. Macdonald, Introduction to commutative algebra, Addison-Wesley, Reading, Mass., 1969.
5. F.V. Atkinson, The reversibility of a differentiable mapping, Canad. Math. Bull. 4 (1961), 161–181.