Sechrest, L. (1979). Unobtrusive measurement today. Jossey-Bass.
Cita Chicago (17th ed.)Sechrest, Lee. Unobtrusive Measurement Today. San Francisco, Calif: Jossey-Bass, 1979.
Cita MLA (9th ed.)Sechrest, Lee. Unobtrusive Measurement Today. Jossey-Bass, 1979.
Atenció: Aquestes cites poden no estar 100% correctes.