Powell, L. S. (1973). Lecturing. Pitman.
Cita Chicago (17th ed.)Powell, Len S. Lecturing. Johannesburg, Union of South Africa: Pitman, 1973.
Cita MLA (9th ed.)Powell, Len S. Lecturing. Pitman, 1973.
Atenció: Aquestes cites poden no estar 100% correctes.