APA (7th ed.) Citation
Hopf, L. (1948). Introduction to the differential equations of physics. [s.n.].
Chicago Style (17th ed.) Citation
Hopf, Ludwig. Introduction to the Differential Equations of Physics. [s.l.]: [s.n.], 1948.
MLA (9th ed.) Citation
Hopf, Ludwig. Introduction to the Differential Equations of Physics. [s.n.], 1948.
Warning: These citations may not always be 100% accurate.