^Sexual Orientation and Gender Expression in Social Work Practice, edited by Deana F. Morrow and Lori Messinger (2006, ISBN0231501862), page 8: "Gender identity refers to an individual's personal sense of identity as masculine or feminine, or some combination thereof."
^V. M. Moghadam, Patriarchy and the politics of gender in modernising societies, in International Sociology, 1992: "All societies have gender systems."
^Carlson, Neil R.; Heth, C. Donald, Sensation, (编) Carlson, Neil R.; Heth, C. Donald, Psychology: the science of behaviour 4th, Toronto, Canada: Pearson: 140–141, 2009, ISBN 9780205645244.
^Jack David Eller, Culture and Diversity in the United States (2015, ISBN1317575784), page 137: "most Western societies, including the United States, traditionally operate with a binary notion of sex/gender"
^For example, "transvestites [who do not identify with the dress assigned to their sex] existed in almost all societies." (G. O. MacKenzie, Transgender Nation (1994, ISBN0879725966), page 43.) — "There are records of males and females crossing over throughout history and in virtually every culture. It is simply a naturally occurring part of all societies." (Charles Zastrow, Introduction to Social Work and Social Welfare: Empowering People (2013, ISBN128554580X), page 234, quoting the North Alabama Gender Center.)