J.N.STAMENOV
Institute for Nuclear Research
and Nuclear Energy
72, Tzarigradsko chaussee, blvd., 1784, Sofia, BULGARIA
J.P.CARBONNEL
Universite Paris VI, Laboratoire de Geologie Applique
75252 Paris Cedex 05, FRANCE
B.I.VACHEV
Institute for Nuclear Research
and Nuclear Energy
72, Tzarigradsko shaussee, blvd., 1784, Sofia, BULGARIA