Media type: E-Article Title: An improvement for the unique existence of a limit cycle of the Duff and Levinson-type system Contributor: Hayashi, Makoto imprint: Hikari, Ltd., 2014 Published in: Applied Mathematical Sciences Language: Not determined DOI: 10.12988/ams.2014.48643 ISSN: 1314-7552 Keywords: Applied Mathematics Origination: Footnote: