@article{JRAM_1970__245_151056,
     author = {Ya Yen Lee Wang},
     title = {On the order of the {Euler-Lagrange} equations of the variational problem of the affine arc length.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {55--62},
     publisher = {mathdoc},
     volume = {245},
     year = {1970},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1970__245_151056/}
}