Please answer the following question: Information:  - The Bluest Eye was written by Toni Morrison in 1970. A single mother of two sons, Morrison wrote the novel while she was teaching at Howard University . She centers the story around a young African American girl named Pecola who grows up during the years following the Great Depression in Lorain, Ohio. Due to her dark skin color, Pecola gets taunted for her appearance as the members of her community associate beauty with "whiteness". She ultimately develops an inferiority complex, which fuels her desire for blue eyes. The point of view switches between the perspective of Claudia MacTeer, the daughter of Pecola's foster parents, and multiple third-person limited viewpoints. Due to the controversial issues the book raises such as racism, incest, and child molestation, there have been numerous attempts to ban it from schools and libraries.  - Princeton University is a private Ivy League research university in Princeton, New Jersey, United States.  - Sula is a 1973 novel by Nobel Prize - winning author Toni Morrison .  - Toni Morrison (born Chloe Ardelia Wofford; February 18, 1931) is an American novelist, editor, and Professor Emeritus at Princeton University. Her novels are known for their epic themes, vivid dialogue, and richly detailed characters. Among her best known novels are "The Bluest Eye" (1970), "Sula" (1973), "Song of Solomon" (1977), and "Beloved" (1987).    What entity does 'sula ' has the relation 'instance of' with?
A:
book