APA (7th ed.) Citation

Hennings, G., & Hennings, D. G. (1976). Keep Earth clean, blue & green: Environmental activities for young people. Citation Press.

Chicago Style (17th ed.) Citation

Hennings, George, and Dorothy Grant Hennings. Keep Earth Clean, Blue & Green: Environmental Activities for Young People. New York: Citation Press, 1976.

MLA (8th ed.) Citation

Hennings, George, and Dorothy Grant Hennings. Keep Earth Clean, Blue & Green: Environmental Activities for Young People. Citation Press, 1976.