Cita APA (7th ed.)
NAGEL, S. (1991). DEALING WITH UNKNOWN VARIABLES IN POLICY / PROGRAM EVALUATION. PERGAMON PRESS.
Cita Chicago (17th ed.)
NAGEL, S. DEALING WITH UNKNOWN VARIABLES IN POLICY / PROGRAM EVALUATION. NUEVA YORK: PERGAMON PRESS, 1991.
Cita MLA (9th ed.)
NAGEL, S. DEALING WITH UNKNOWN VARIABLES IN POLICY / PROGRAM EVALUATION. PERGAMON PRESS, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.