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Otero, Daniel E. 2019. Completing the Square: From the Roots of Algebra, A Mini-Primary Source Project for Students of Algebra and Their Teachers. *Convergence* 16 (September). DOI:10.4169/convergence20190901.

The author wishes to thank the *Convergence* editorial board and anonymous reviewers for their helpful comments on earlier drafts.

Günhan Caglayan (MR Author ID: 1116420) teaches mathematics at New Jersey City University. His main interests are mathematical visualization and student learning through modeling and visualization.