. . . . "The personalized system of instruction in higher education: readings on PSI, the Keller plan" . . "The personalized system of instruction in higher education: readings on PSI--the Keller plan"@en . "The personalized system of instruction in higher education: readings on PSI--the Keller plan" . . . . . . . . "Enseignement programmé." . . "Enseignement programmé" .