1. Elementary Science Study (ESS), Education Development Center, Webster Division, McGraw-Hill Book Company, Manchester, Missouri.
2. Science—A Process Approach, The American Association for the Advancement of Science, Xerox Corporation, New York.
3. Science Curriculum Improvement Study. (SCIS) Science Curriculum Improvement Study, University of California, Berkeley, Rand McNally, Chicago, Illinois.
4. An experimental comparison of urban children with suburban children on eight tasks of basic skills
5. The relationship of teacher-pupil critical-thinking ability