Circle-preserving transformations in Finsler spaces
  Here, by extending the definition of circle to Finsler geometry, we show that, every circle-preserving local diffeomorphism is conformal. This result implies that in Finsler geometry, the definition of concircular change of metrics, a priori, does not require the conformal assumption. 
Behroz Bidabad, Zhongmin Shen
math.DG