Olena KONOVALOVA, Olha SHCHERBAKOVA, Tetiana OMELKOVETS, Mariia KALISTA, Iryna HURTOVETKO, Natalia SYDORA, Kateryna NOVOSAD. Study of petiolary anatomical features of common oak (Quercus robur L.) and red oak (Quercus rubra L.) and their significance for microdiagnostics of raw materials