Gadjalska, N., R. Kireva, V. Subkova, G. Patamanska, M. Moteva, V. Branicheva, E. Grancharova, and K. Karaivanov. 2015. “The Irrigation Effectiveness of Chernozems”. Bulgarian Journal of Soil Science, Agrochemistry and Ecology 49 (3): 11-21. https://agriacad.eu/ojs/index.php/bjssae/article/view/2253.