• A characterization of isochronous centres in terms of symmetries 

      Freire, Emilio; Gasull Embid, Armengol; Guillamon Grabolosa, Antoni (2000)
      Article
      Accés obert
      We present a description of isochronous centres of planar vector fields $X$ by means of their groups of symmetries. More precisely, given a normalizer $U$ of $X$ (i.e., $[X,U]=\mu X$, where $\mu$ is a scalar function), we ...