**1**- P. Erdos, P. Frankl and Z, Füredi, ``Families of finite
sets in which no set is covered by the union of
*r*others,''*Israel J. of Mathematics,*vol. 51, nos. 1-2, pp. 79-89, 1985. **2**- M. Ruszinkó, ``On the upper bound of the size of the
*r*-cover-free families,''*Journal of Combinatorial Theory, Series A*vol. 66, no. 2, pp. 302-310, May 1994. **3**- Z. Füredi, M. Ruszinkó, An improved upper bound of the rate
of Eucledian superimposed codes,
*Proceedings of the 1998 IEEE International Symposium on Information Theory,*August 16-21, MIT, Cambridge; also accepted for publication in*IEEE Transactions on Information Theory.*

Tue Jan 12 12:24:55 EST 1999