About this article
Published Online: Dec 30, 2019
Page range: 249 - 252
DOI: https://doi.org/10.12775/eec.2019.010
© 2019 Gerd Vonderach, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.
Gerd Vonderach