"Batgirl was soon popular enough to appear regularly over the next two decades and Yvonne Craig certainly made an impression on many viewers with her one season portraying young Ms. Gordon." Similarly, Cronin states that following the publication of The Killing Joke, Barbara Gordon—in her new persona as Oracle—became "more popular, in fact, than she was when she was Batgirl. She even gained her own title, Birds of Prey, about her and a group of superhero operatives she organizes[.]" The character has been the subject of analysis in academia, regarding the portrayal of women, librarians, and disabled people in mainstream media. Throughout the character's history, Barbara Gordon's intelligence has been one of her defining attributes. According to BusinessWeek, she is listed as one of the top ten most intelligent fictional superheroes appearing in American comics and is the only female character to appear on the list. In 2011, Barbara Gordon was ranked 17th in both IGN's "Top 100 Comic Book Heroes" and Comics Buyer's Guides "100 Sexiest Women in Comics". Feminist interpretations In The Supergirls: Fashion, Feminism, Fantasy, and the History of Comic Book Heroines (2009), author Mike Madrid states that what set Barbara Gordon as Batgirl apart from other female characters was her motivation for crime-fighting. Unlike Batwoman who preceded her, "she wears his symbol on her chest, but she is not his girlfriend or faithful handmaiden." Because she does not pursue a romantic interest in Batman, "Batgirl is a female Batman can actually regard as a brilliant peer and a partner in the war on crime, the same way he would a male." Historian Peter Sanderson observed that while "Barbara Gordon initially conformed to hackneyed stereotypes as a dowdy librarian ... her transformation into Batgirl could be seen in retrospect as a symbol of the emerging female empowerment movement of the 1960s. (Moreover, by the 1970s Barbara had given herself a makeover even in her 'civilian identity and ran for Congress.)" In the 1980s, Barbara Kesel, after writing a complaint to DC Comics over the negative portrayal of female characters, was allowed to write for Barbara Gordon in Detective Comics. Robin Anne Reid, in Women in Science Fiction and Fantasy: Overviews (2009), wrote that "Kesel's version of Batgirl established her as a character separate from Batman and Robin: a woman motivated to do what men do, but alone and in her own way. Her Secret Origins (1987) and