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2. Twins: behavioral differences;Brown;Child Developm.,1967
3. The DCR-II Event Recorder: a portable high-speed digital cassette system with direct computer access;Celhoffer;Behav. Res. Meth. Instrument.,1977
4. Personality development in twins;Cohen;This Journal,1972
5. Egeland, B., Tavaldson, B. & Brunquell, D. (1977), Observations of waiting room and feeding interactions (mimeographed report), Minneapolis: University of Minnesota.