1. Arnett, W. D.: 1971,Astrophys. J. 166, 153.
2. Baity, W. H., Teegarden, B., Lezniak, J. A., and Webber, W. R.: 1971,Astrophys. J. 164, 521.
3. Cameron, A. G. W.: 1969, in L. H. Ahrens (ed.),Origin and Distribution of the Elements, Pergamon, London, p. 125.
4. Cartwright, B. G., Garcia Munoz, M., and Simpson, J. A.: 1971,12th Int. Conf. on Cosmic Rays, Hobart 1, 215.
5. Casse, M. M.: 1971, Research Report Centre D'Études Nucleaires de Saclay.