Authors are (Clockwise from upper left):

Toni Morrison
Leslie Marmon Silko
Edward Albee
Gerald Vizenor*
John Muir
Plato
Louise Erdrich
Maxine Hong Kingston
Virginia Woolf
Samuel Beckett
Dorothy Allison
Frederick Douglass
Gwendolyn Brooks
Monique Wittig**
Christopher Marlowe
William Shakespeare

* Photo courtesy of the author's official website  
**Photo courtesy of the University of Arizona website