@article{AM2_1975__12_136512,
     author = {Gregory Walter Horndeski},
     title = {Sufficiency {Conditions} {Under} {Which} a {Lagrangian} is an {Ordinary} {Divergence.}},
     journal = {Aequationes mathematicae},
     pages = {232--241},
     publisher = {mathdoc},
     volume = {12},
     year = {1975},
     zbl = {0311.49030},
     url = {http://geodesic.mathdoc.fr/item/AM2_1975__12_136512/}
}