Authors
Carmen Coll
Institute of Multidisciplinary Mathematics, Polytechnic University of Valencia (UPV), Valencia, Spain
Elena Sánchez
Institute of Multidisciplinary Mathematics, Polytechnic University of Valencia (UPV), Valencia, Spain
© 2019 Carmen Coll, Elena Sánchez, published by University of Zielona Góra
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.