1. Conservation of illusion-distorted identity: Its relation to MA and CA in normals and retardates;Achenbach;Child Development,1969
2. Surprise and GSR as indicators of conservation: A new approach to developmental diagnosis with young children;Achenbach,1970
3. Surprise and memory as indices of concrete operational development;Achenbach;Psychological Reports,1973
4. Investigation and maintenance of curiosity behavior as a function of surprise versus novel and familiar stimuli;Charlesworth;Child Development,1964
5. Cognitive structures related to the principle of conservation;Engelmann,1967