*{{cite journal|first1=J.|last1=Llibre|first2=C.|last2=Valls|author2-link= Clàudia Valls |title=Global analytic first integrals for the real planar Lotka-Volterra system|journal=J. Math. Phys.|volume=48|issue=3|pages=033507|year=2007|doi=10.1063/1.2713076|bibcode=2007JMP....48c3507L}} | *{{cite journal|first1=J.|last1=Llibre|first2=C.|last2=Valls|author2-link= Clàudia Valls |title=Global analytic first integrals for the real planar Lotka-Volterra system|journal=J. Math. Phys.|volume=48|issue=3|pages=033507|year=2007|doi=10.1063/1.2713076|bibcode=2007JMP....48c3507L}} |