1. L.I. Schiff, Quantum Mechanics, 3rd edn. ( McGraw-Hill, New York 1968 )
2. H.S.W. Massey, E.H.S. Burhop, Electronic and Ionic Impact Phenomena, Vol. 1 (Clarendon, Oxford 1969 ) Sect. 6. 3
3. C. Ramsauer, Ann. Phys. 64, 513 (1921); ibid. 66, 545 (1921)
4. C. Erginsoy, Phys. Rev. 79, 1013 (1950)
5. S.H. Koenig, R.D. Brown III, W. Schillinger, Phys. Rev. 128, 1668 (1962)