Authors
Yukio Ohkubo
Dept. of Businessv Administration, The International University of Kagoshima, Kagoshima, Japan
Oto Strauch
Institue of Mathematics, Slovak Academy of Sciences, Bratislava, Slovakia
© 2020 Yukio Ohkubo, Oto Strauch, published by Slovak Academy of Sciences, Mathematical Institute
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.