@article{ND_2008_4_2_a3,
     author = {V. V. Kozlov},
     title = {Lagrange's identity and its generalizations},
     journal = {Russian journal of nonlinear dynamics},
     pages = {157--168},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {2008},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ND_2008_4_2_a3/}
}