S. Bereg, M. Völker, A. Wolff, и Y. Zhang. Proc. 33rd Int. Conf. Current Trends Theory &
Practice Comput. Sci. (SOFSEM'07), том 4362 из Lecture Notes in Computer Science, стр. 177--186. Springer-Verlag, (2007)
J. Just, и H. Siller. Twelfth Congress of the European Society for Research in Mathematics Education (CERME12), том TWG26 из Congress of the European Society for Research in Mathematics Education (CERME12), Bozen-Bolzano, Italy, (февраля 2022)