References
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- Kalajdzievski, S. (2000). Some evident summation formulas. The Mathematical Intelligencer, 22(3), 47–49. https://doi.org/10.1007/BF03025282
- Nelsen, R. B. (1993). Proofs without words: Exercises in visual thinking. Number v. 1 in classroom resource materials. Mathematical Association of America.
- Nelsen, R. B. (2000). Proofs without words II. Classroom resource materials. Mathematical Association of America.
- Nelsen, R. B. (2016). Proofs without words III: Further exercises in visual thinking. Classroom resource materials. Mathematical Association of America.