Keller, Sophie. "1st Grade Math Lesson". OER Commons. Institute for the Study of Knowledge Management in Education, 11 Feb. 2019. Web. 26 Dec. 2024. <https://oercommons.org/authoring/51970-1st-grade-math-lesson>.
Keller, S. (2019, February 11). 1st Grade Math Lesson. OER Commons. Retrieved December 26, 2024, from https://oercommons.org/authoring/51970-1st-grade-math-lesson.