Cita APA (7a ed.)

Helms, L. L. (1969). Introduction to potential theory. Wiley-Interscience.

Cita Chicago Style (17a ed.)

Helms, L. L. Introduction to Potential Theory. New York [etc.]: Wiley-Interscience, 1969.

Cita MLA (9a ed.)

Helms, L. L. Introduction to Potential Theory. Wiley-Interscience, 1969.