Cita APA (7th ed.)

Piaget, J., & Ackermann-Valladao, E. (1987). Possibility and necessity. University of Minnesota Press.

Cita Chicago (17th ed.)

Piaget, Jean, i E. Ackermann-Valladao. Possibility and Necessity. Minneapolis: University of Minnesota Press, 1987.

Cita MLA (9th ed.)

Piaget, Jean, i E. Ackermann-Valladao. Possibility and Necessity. University of Minnesota Press, 1987.