1. Chen Ning Yang, The law of parity conservation and other symmetry laws of physics; Tsung Dao Lee, Weak interactions and nonconservation of parity, Nobel Lectures, Physics 1942–1962,Elsevier, Amsterdam, 1964, pp. 393–403 and pp. 406–418.
2. See, for instance, A. C. Crombie, Augustine to Galileo,Falcon Press, London, 1952, pp. 316 ff. The growth of the understanding of the realm of the explainable, from the end of the 13th century on, can be traced through almost every chapter of this book.
3. C.F. v. Weizsäcker, Z. Astrophys.,22 (1944) 319
4. S. Chandrasekhar, Rev. Mod. Phys., 18 (1946) 94.
5. An interesting and well understood case is that of « focussing collisions » in which neutrons, having velocities which are rather high but with random orientation, are converted into lower velocity neutrons but with preferential directions of motion. See R. H. Silsbee, J. Appl.Phys.,28 (1957) 1246