6Yammarino, F &Dansereau. F. 2002. The Many Faces of Multi - Level Issues: Research in Multi - Level Issues. Volume 1 [M]. Amsterdam JAI Press. 95-100.
7Tice, J. 1997. The mixed ability class [ M]. London: Richmond Publishing.
8Bbom. B. S. 1981. All Our Children Learning [M]. New York: McGraw - Hill.