TY JOUR TI OPTIMIZATION OF BIOACTIVE SUBSTANCES OBTAINING IN AQUEOUS ALCOHOL EXTRACTS OF ASPEN BARK KW aspen bark KW biologically active substances KW extraction KW aqueous-alcoholic extracts KW extractive substances KW experiment planning matrix JO Bulletin of KSAU AU Soboleva, S.V. AU Chentsova, L.I. AU Pochekutov, I.S. PY 2012 IS PB Krasnoyarsk State Agrarian University