Velev, Nikolay, Iva Apostolova, Zuzana Rozbrojová, and Petra Hájková. 2015. “The Alliances Arrhenatherion, Cynosurion and Trifolion Medii in Western Bulgaria – Environmental Gradients and Ecological Limitations”. Hacquetia 9 (2). https://ojs.zrc-sazu.si/hacquetia/article/view/2894.