Who is Barbara Smith, Cathy McCandless, Carol Hanisch, Phyllis Ches from Feminist Theory from Margin to Center and what is their importance?

Authors, Barbara Smith, Cathy McCandless, Carol Hanisch, and Phyllis Ches are cited by the author throughout the book. It's important to note that not all of these women support of the author's theories. She often cites works by authors whose theories oppose and/or contradict her own.