APA (7th ed.) Citation

Nørgaard, E., & Hildesheim, E. (1971). The book of balloons. Crown Publishers.

Chicago Style (17th ed.) Citation

Nørgaard, Erik, and Erik Hildesheim. The Book of Balloons. New York: Crown Publishers, 1971.

MLA (9th ed.) Citation

Nørgaard, Erik, and Erik Hildesheim. The Book of Balloons. Crown Publishers, 1971.