@article{701543,
     title = {Natural transformations of Lagrangians},
     booktitle = {Proceedings of the Winter School "Geometry and Physics"},
     series = {GDML\_Books},
     publisher = {Circolo Matematico di Palermo},
     address = {Palermo},
     year = {1994},
     pages = {[41]-46},
     mrnumber = {MR1343999},
     zbl = {0839.58025},
     url = {http://dml.mathdoc.fr/item/701543}
}

Dębecki, Jacek. Natural transformations of Lagrangians, dans Proceedings of the Winter School "Geometry and Physics", GDML_Books,  (1994), pp. [41]-46. http://gdmltest.u-ga.fr/item/701543/