In 1965 King and Hayden expanded on this paper, elaborating on its central thesis that not only in society at large, but also within the civil rights movement itself, women are "caught" in a "common-law caste system" that limits their opportunity and voice. King and Hayden sent "Sex and Caste - A Kind of Memo" to forty women activists across the U.S. These women were involved in organizations such as Students for a Democratic Society, the National Student Association, the Northern Student Movement, the Student Peace Union, and SNCC. The document was subsequently published under the title "Sex and Caste" in the pacificst periodical Liberation, and entreated women to "start to talk with each other more openly."