1. J ED PSYCHOL 12: 123 (1921).
2. J ED PSYCHOL 12: 195 (1921).
3. J ED PSYCHOL 12: 271 (1921).
4. BALTES, P.B., NEW PERSPECTIVES ON THE DEVELOPMENT OF INTELLIGENCE IN ADULTHOOD - TOWARD A DUAL-PROCESS CONCEPTION AND A MODEL OF SELECTIVE OPTIMIZATION WITH COMPENSATION, LIFE-SPAN DEVELOPMENT AND BEHAVIOR 6: 33 (1984).
5. BERRY, J.W., CHANGING CONCEPTIONS: 35 (1984).