@article{INTG_1991_23_a2,
     author = {I. Kol\'a\v{r}},
     title = {Natural bundles and operators},
     journal = {Itogi Nauki i Tekhniki. Seriya Problemy Geometrii. Trudy Geometricheskogo Seminara},
     pages = {67--98},
     year = {1991},
     volume = {23},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTG_1991_23_a2/}
}