APA (7th ed.) Citation

Butzer, P. L., & Berens, H. (1967). Semi-groups of operators and approximation. Springer.

Chicago Style (17th ed.) Citation

Butzer, Paul Leo, and Hubert Berens. Semi-groups of Operators and Approximation. Berlin: Springer, 1967.

MLA (9th ed.) Citation

Butzer, Paul Leo, and Hubert Berens. Semi-groups of Operators and Approximation. Springer, 1967.