Lopushniak, V., and G. Hrytsulyak. “Impact of Sewage Sludge Application on the Humus State of Sod-Podzolic Soil of Subcarpathia under Energetic Willow Plantation”. Agricultural Science and Practice, Vol. 3, no. 2, July 2016, pp. 26-31, doi:10.15407/agrisp3.02.026.