Gerald Holton«Robert K. Merton - Biographical Memoirs».Proceedings of the American Philosophical Society,148,4,04-12-2004,p.506–517[Consulta: 7 agost 2007].«He developed a theory of the reference group (i.e., the group to which individuals compare themselves, which is not necessarily a group to which those individuals belong), and elaborated on the concepts of in-group and out-group.»