Ljubenova, M. “Above-Ground Energy Reserves and Annual Accumulation of Energy in Shrub and Herb Layers in Ass. Quercus frainetto+Quercus Cerris - Festuca heterophylla+Poa Nemoralis in the Vakarel Mountains”. Macedonian Journal of Ecology and Environment, vol. 2, no. 1, Aug. 1994, pp. 29-35, https://mjee.org.mk/index.php/mjee/article/view/12.