@article{701533,
     title = {Natural 2-forms on the tangent bundle of a Riemannian manifold},
     booktitle = {Proceedings of the Winter School "Geometry and Topology"},
     series = {GDML\_Books},
     publisher = {Circolo Matematico di Palermo},
     address = {Palermo},
     year = {1993},
     pages = {[165]-174},
     mrnumber = {MR1283629},
     zbl = {0818.53020},
     url = {http://dml.mathdoc.fr/item/701533}
}

Janyška, Josef. Natural 2-forms on the tangent bundle of a Riemannian manifold, dans Proceedings of the Winter School "Geometry and Topology", GDML_Books,  (1993), pp. [165]-174. http://gdmltest.u-ga.fr/item/701533/