Step-s involutive families of vector fields, their orbits and the   Poincar\'e inequality
  We consider a family of $C^1$ vector fields satisfying a suitable higher order involutivity condition. We discuss the definition of commutators, the regularity of Sussmann's orbits and the Poincar\'e inequality. 
Annamaria Montanari and Daniele Morbidelli
math.CA math.DG