**Acknowledgements**

Since 2012, our research of small glaciers has been widely supported by the South-west University "Neofit Rilski", Bulgaria, through the projects: SRP-B3 'New research in the fields of Chemistry, Geography and Environment', 2012; SRP-B4 'Modelling of biological and ecological activities with the aid of chemical and mathematical methods', 2013; SRP-B3 'Mathematical and empirical methods and approaches in chemical research and environmental protection', 2014; SRP-A10 'Complex research of present-day small glaciers on the Balkan peninsula', 2015; RP-B4/16 'Mathematical and computer modelling in natural sciences', 2016. Our work in 2009, 2010 and 2012–2014 was supported by the Bulgarian Academy of Sciences (the National Institute of Geophysics, Geodesy and Geography). Our measurements in Pirin were helped also by prof. Predrag Djurović from the Faculty of Geography of the University of Belgrade, Serbia (2013) and by Brigitte Magori and Flavius Sorin-Sirbu from the West University of Timisoara, Romania. Special thanks to Assoc. Prof. Dr Michail Mihailov from our department, who gave a vital support for our work.
