Bulgaria
Sofia - 1113
National Institute of Geophysics, Geodesy and Geography - BAS	
Acad. G. Bonchev Str., block 3  
Petar Stefanov -  Experimental Laboratory of Karstology	 
Tel. +3592 971 30 05; +3592 971 33 75
E-mail: p_stefanov@prokarstterra.bas.bg; 
        psgeo@abv.bg