Published Online: Dec 31, 2018
Page range: 11 - 15
DOI: https://doi.org/10.2478/poljes-2018-0002
© 2019 Wioleta Danilewicz, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Wioleta Danilewicz
University of Bialystok,Bialystok, Poland