1. The philosophical aspects are discussed in J. D. Barrow.The World Within the World (Oxford University Press, Oxford, 1988), p. 111. from the view that “Ideally a description of how Nature operates should not depend on the observer.”
2. J. L. Johnson, “Toward a fundamental image preprocessor.”App. Opt. 29 (32). 4819 (1990).
3. R. Gilmore.Lie Groups, Lie Algebras, and Some of Their Applications (Wiley, New York, 1974), p. 453.
4. E. M. Loebl,Group Theory and Its Applications (Academic, New York. 1971), p. 185.
5. V. Heine,Group Theory in Quantum Mechanics (Pergamon, Oxford. 1960), pp. 356–367.