Natural transformations of second tangent and cotangent functors Ivan Kolář, Zbigniew Radziszewski (1988) Czechoslovak Mathematical Journal
Nonholonomic tangent spaces: intrinsic construction and rigid dimensions. Agrachev, A., Marigo, A. (2003) Electronic Research Announcements of the American Mathematical Society [electronic only]
Nonlinear connections and semisprays on tangent manifolds. Crâşmăreanu, Mircea (2003) Novi Sad Journal of Mathematics