Electrodynamics (2nd Ed.). New York: John Wiley & Sons, Inc. ISBN 0-471-43132-X. LeonardI. Schiff (1968). Quantum mechanics (3rd ed.). London : McGraw-Hill.
ISBN 0-521-55506-X Schiff, LeonardI., Quantum Mechanics 3rd, McGraw–Hill, 1968 Weinberg, Steven, The Quantum Theory of Fields. Volume I: Foundations, Cambridge