@article{MAN_1994__299_4_165205,
     author = {Ian M. Anderson and Juha Pohjanpelto},
     title = {Variational principles for differential equations with symmetries and conservation laws. {I.} {Second} order scalar equations.},
     journal = {Mathematische Annalen},
     pages = {191--222},
     publisher = {mathdoc},
     volume = {299},
     number = {4},
     year = {1994},
     zbl = {0804.49030},
     url = {http://geodesic.mathdoc.fr/item/MAN_1994__299_4_165205/}
}