Cita APA (7a ed.)

Tillich, P., & Sardelli, G. (1964). The courage to be ([2nd impression].). Collins.

Cita Chicago Style (17a ed.)

Tillich, Paul, y Giuseppe Sardelli. The Courage to Be. [2nd impression]. London [etc.]: Collins, 1964.

Cita MLA (9a ed.)

Tillich, Paul, y Giuseppe Sardelli. The Courage to Be. [2nd impression]. Collins, 1964.