1. E. Anassontzis, 1994, Nuclear Instruments and Methods
A349, 242.
2. Berezinski, 1990, Astrophysics of Cosmic Rays, North Holland.
3. A. Bottino, 1992, Fourth International Workshop on NEUTRINO TELESCOPES, M.Baldo Ceolin, editor, Venice.
4. Demidova, 1992, 2nd NESTOR International Workshop, L.K. Resvanis, editor.
5. Di Credico, 1993, contributed paper to the Calgary 1993 cosmic ray conference by the MACRO collaboration.