1. Agrawal, S. P. and Singh, R. L.: 1975,14th Int. Cosmic-Ray Conf. (M�nchen) 4, 1193.
2. Ananth, A. G., Agrawal, S. P. and Rao, U. R.: 1974,12th Int. Cosmic Ray Conf. (Hobart) 2, 651.
3. Ananth, A. G., Agrawal, S. P. and Rao, U. R.: 1974,Pramana,3, 74.
4. Bussoletti, E.: 1973,Eldo-Cesles/Esro-Cers Scient. Tech. Rev. 5, 285.
5. Bussoletti, E., Iucci, N. and Villoresi, G.: 1972,Nuovo Cimento 10B, 43.