@article{JLT_1999_9_1_a10,
     author = {S. Walcher},
     title = {Multi-Parameter {Symmetries} of {First} {Order} {Ordinary} {Differential} {Equations}},
     journal = {Journal of Lie theory},
     pages = {249--269},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {1999},
     url = {http://geodesic.mathdoc.fr/item/JLT_1999_9_1_a10/}
}