2Maver, RE. (2003). Learninlz and Instruction(M). New Jersey: Merrill Prentice Hall.pp.308-313.
3Atkinson&.K,Derrv,S. J,Renkl,A, Wortham,D.(2000).Learning from examples: instructional principles from the worked examples research. Review of Educational Research(J),Vol.72 No.2,pp. 181-214.