APA (7th ed.) Citation

Freundlich, E. The foundations of Einstein's theory of gravitation.

Chicago Style (17th ed.) Citation

Freundlich, Erwin. The Foundations of Einstein's Theory of Gravitation.

MLA (9th ed.) Citation

Freundlich, Erwin. The Foundations of Einstein's Theory of Gravitation.

Warning: These citations may not always be 100% accurate.