1. R.M. Bianchini - G. Stefani “Multivalued fields and control systems withunbounded controls” Ricerche di Automatica 12 (1981) pp. 33–49.
2. A. Haefliger “Varietees feuilletees” Annali della Scuola Norm. Sup. PisavolXVI (1962) pp. 367–397
3. C. Lobry - “Sur l‘ensemble des points atteignables par les solutions d’uneequation differentielle multivoque” Plub. Math. Bordeaux Annee I, Fasc. 5(1973) pp. 43–60.
4. N. Kalouptsidis - D.L. Elliot “Accessibility properties of smooth nonlinearcontrol system” AMES Research Centre 1976, Martin & Hermann ed., Math.Sci. Press, Brookline, (1977) pp. 439–446.
5. P. Stefan - “Accessible sets, orbits and foliations with singularities” Proc.London Math. Soc. 29 (1974) pp. 699–713.