5Sobel M. A. Concept Learning in Algebra [J]. The Mathematics Teacher, 1956, (6).
6Zadeh L.A. Fuzzy Sets [J]. Information and Control, 1965, (3).
7Wedege T. To Know or Not to Know: Mathematics, That Is a Question of Context [J]. Educational Studies in Mathematics, 1999, (1).
8Steinbring H. Analyzing Mathematical Teaching-Learning Situations: The Interplay of Communicational and Epistemological Constraints[J]. Educational Studies in Mathematics, 2005, ( 1 ).
9Cobb P and Bowers J. Cognitive and Situated Learning Perspectives in Theory and Practice [J]. Educational Researcher, 1999, (2).
10Roth W. M. Situating Cognition [J]. The Journal of the Leaming Sciences, 2001, ( 1 ).
