Twin research for everyone [electronic resource] : from biology to health, epigenetics, and psychology / edited by Adam D. Tarnoki, Medical Imaging Centre, Semmelweis University, Hungarian Twin Registry, Budapest, Hungary, David L. Tarnoki, Medical Imaging Centre, Semmelweis University, Hungarian Twin Registry, Budapest, Hungary, Jennifer R. Harris, Centre for Fertility and Health, The Norwegian Institute of Public Health, Oslo, Norway, Nancy L. Segal, Department of Psychology, California State University, Fullerton, CA, United States.