C. Bauer. European university studies: Series 5, Economics and management Peter Lang, Frankfurt am Main, Berlin, Bern, Bruxelles, New York, Oxford, Wien, (2010)
J. Zhang, Y. Dong, Y. Wang, J. Tang, and M. Ding. Proceedings of the 28th International Joint Conference on Artificial Intelligence, page 4278–4284. AAAI Press, (Aug 10, 2019)
J. Smith, and P. Thompson. Employing children's natural powers to build algebraic reasoning in the context of elementary mathematics, Erlbaum, New York, (2007)
M. Cerulli, E. Chioccariello, and E. Lemut. Proceedings of CERME 4, Fourth Congress of the European Society for Research in Mathematics Education 17 - 21 February 2005 in Sant Feliu de Guíxols, Spain YERME day: 16- 17 February., ERME, (February 2005)
M. Cerulli, A. Chioccariello, and E. Lemut. Proceedings of the Fourth Congress of the European Society for Research in Mathematics Education (CERME 4), page 591-600. Sant Feliu de Guíxols, Spain,, (2005)
K. Radinsky, and N. Ailon. Proceedings of the Fourth ACM International Conference on Web Search and Data Mining, page 105--114. New York, NY, USA, ACM, (2011)