[EXPERIENCE IN IMPROVING THE SANITARY STATE OF THE VELIKAYA RIVER IN THE BOUNDARIES OF PSKOV].
D004957:Estonia; D045483:Rivers; D014586:USSR; D014876:Water Pollution; D014881:Water Supply
ESTONIA; USSR; WATER POLLUTION; WATER SUPPLY
OPYT ULUCHSHENIIA SANITARNOGO SOSTOIANIIA REKI VELIKO I V CHERTE PSKOVA.