APA (7th ed.) Citation

Wahl, J., & Wahl, S. (1976). I can count the petals of a flower. NCTM.

Chicago Style (17th ed.) Citation

Wahl, John, and S. Wahl. I Can Count the Petals of a Flower. Reston, Virginia: NCTM, 1976.

MLA (9th ed.) Citation

Wahl, John, and S. Wahl. I Can Count the Petals of a Flower. NCTM, 1976.