1. NCTM, Principles and Standards for School Mathematics (National Council of Teachers of Mathematics United States of America, 2000).
2. D.H. Clements and M.T. Battista, in Handb. Res. Math. Teach. Learn. A Proj. Natl. Counc. Teach. Math., edited by D.A. Grouws (National Council of Teachers of Mathematics, Virginia, 1992), pp. 420–464.
3. Linking the Van Hiele Theory to Instruction
4. Sugiman and E. Apino, “Silent method for mathematics instruction: An overview of teaching subsets”, in Mathematics, Science, and Computer Science Education (MSCEIS)-2016, AIP Conference Proceedings. 1848, (American Institute of Physics, Melville, NY, 2017), pp. 040015(1-6).
5. H.D. Brown, Principles of Language Learning and Teaching (Prentice Hall, Englewood Cliffs, NJ, 1991), pp. 45.