[1]. Akyuz, Didem. (2012). “The Value of Debts and Credits.” Mathematics Teaching in the Middle School, 17(6): 332-8.
 [2]. Ball, Deborah L., Thames, Mark H. and Phelps, Geoffrey. (2008). “Content Knowledge for Teaching: What makes it special?” Journal of Teacher Education, 59: 389-406. 
 [3]. Common Core State Standards Initiative (CCSSI). (2010). Common Core State Standards for Mathematics.
Washington, DC: National Governors Association Center for Best Practices and the Council of Chief State School Officers.
http://www.corestandards.org/assets/CCSI_Math%20Standards.pdf 
 [4]. Fennema, E., Franke, M. L., Carpenter, T.P., & Carey, D. A. (1993). Using children's mathematical knowledge in
instruction. American Educational Research Journal, 30(3): 403-34. 
[5]Greeno, J. G. (1993). For research to reform education and cognitive science. In L.A. Penner, G.M. Batsche, H.M. Knoff, &  D.L. Nelson (Eds.), The challenge in mathematics and science education: Psychology's response. 153-92. Washington, DC:
American Psychological Association. 
 [6]. Kerrigan, Nancy & Spencer, Mary. (2003). Artistry on Ice: Figure Skating Skills and Style. Human Kinetics: Champaign, IL. 
 [7]. Posamentier, Alfred S. (2003). Math Charmers: Tantalizing Tidbits for the Mind.Prometheus Books. 
 [8]. United States Figure Skating. (2013). http://usfsa.org/content/FactSheet.pdf