Authors
Katerina Gabrovska-Evstatieva
Ruse University “Angel Kanchev”,, Ruse, Bulgaria
Boris Evstatiev
Ruse University “Angel Kanchev”,, Ruse, Bulgaria
© 2017 Ivan Beloev, Katerina Gabrovska-Evstatieva, Boris Evstatiev, published by Slovak University of Agriculture in Nitra
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.