APA
(11991). Proceedings of the National Academy Of Sciences of the United States of America. U.S.A: Proc. Natl. Acad. Sci.
Chicago
11991. Proceedings of the National Academy Of Sciences of the United States of America. U.S.A: Proc. Natl. Acad. Sci.
Harvard
(11991). Proceedings of the National Academy Of Sciences of the United States of America. U.S.A: Proc. Natl. Acad. Sci.
MLA
Proceedings of the National Academy Of Sciences of the United States of America. U.S.A: Proc. Natl. Acad. Sci. 11991.