Johnson, K., & Herr, T. (2001). Problem solving strategies: Crossing the river with dogs and other mathematical adventures. Key Curriculum Press.
Chicago-viite (17. p.)Johnson, Ken, ja Ted Herr. Problem Solving Strategies: Crossing the River with Dogs and Other Mathematical Adventures. Emeryville, Calif: Key Curriculum Press, 2001.
MLA-viite (9. p.)Johnson, Ken, ja Ted Herr. Problem Solving Strategies: Crossing the River with Dogs and Other Mathematical Adventures. Key Curriculum Press, 2001.
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