Unpublished Notes 5)  Calculus lemma:  Smooth functions vanishing on a submanifold 4)   Stable submanifolds of Pfaffian systems 3)  Chong-Kyu Han,  Finiteness of multi-contact maps for 2n vector fields on R^{2n+1},  preprint, presented in Banff conference of CR geometry, May 2006,   PDF 2)  Frobenius theorem with singular torsions 1) Infinitesimal Iosmetries on (M^2, g)