Source: Adapted from: Hill Goldsmith, H. (1991). A zygosity questionnaire for young twins: A research note. Behavior Genetics, 21(3), 257-269. [URL link]; Onisczenko, W., Angleitner, A., Strelau, J., & Angert, T. (1993). The questionnaire of twins' physical resemblance. Unpublished Manuscript. University of Warsaw, Poland and University of Bielefeld, Germany.
Source: Adapted from: Hill Goldsmith, H. (1991). A zygosity questionnaire for young twins: A research note. Behavior Genetics, 21(3), 257-269. [URL link]; Onisczenko, W., Angleitner, A., Strelau, J., & Angert, T. (1993). The questionnaire of twins' physical resemblance. Unpublished Manuscript. University of Warsaw, Poland and University of Bielefeld, Germany.