− | | institutionen = Pädagogische Hochschule Freiburg, Foundation for research and technology (FORTH) EL, University of Utrecht, University of Nottingham, University of Jaen, University of Nicosia , University of Athens, Hogskolen i Sor-Trondelag, Universität Kiel, Babeş-Bolyai University – Cluj Napoca, University of Hradec Králové, Divulgación Dinámica SL – Seville, Hacettepe University, Vilnius University, Universität Innsbruck, Gutenberg Universität Frankfurt, Institute of Mathematics and Informatics of the Bulgarian Academy of Sciences | + | | institutionen = Pädagogische Hochschule Freiburg, Foundation for research and technology (FORTH) EL, University of Utrecht, University of Nottingham, University of Jaen, University of Nicosia , University of Athens, Hogskolen i Sor-Trondelag, Universität Kiel, Babeş-Bolyai University – Cluj Napoca, University of Hradec Králové, Divulgación Dinámica SL – Seville, Hacettepe University, Vilnius University, Universität Innsbruck, Universität Frankfurt, Institute of Mathematics and Informatics of the Bulgarian Academy of Sciences |