About this article
Published Online: Dec 22, 2018
Page range: 121 - 128
DOI: https://doi.org/10.2478/mgrsd-1990-040116
© 2018 Andrzej Lisowski, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.
Andrzej Lisowski