APA question - author's name

One of the authors of the article I am reviewing is listed as "Nancy Jo Dunn".  The other authors are listed by their first name, initial, and last name, such as "Nancy J. Peterson" and "Sara D. Bailey".  Since it appears that Nancy Jo may be her first name, and Jo is not her middle name, should I list her as "Dunn, N." or as "Dunn, N. J." ?  Or since it is not hyphened as "Nancy-Jo" should I assume Jo is her middle name?