@article{MAN_1992__292_2_164921,
     author = {N. Kamran and J.C. Hurtubise},
     title = {Projective connections, double fibrations and formal neighbourhoods of lines.},
     journal = {Mathematische Annalen},
     pages = {383--410},
     publisher = {mathdoc},
     volume = {292},
     number = {2},
     year = {1992},
     zbl = {0738.58051},
     url = {http://geodesic.mathdoc.fr/item/MAN_1992__292_2_164921/}
}