González López, ArtemioKamran, NikyOlver, Peter J.2023-06-202023-06-201992-120002-932710.2307/2374757https://hdl.handle.net/20.500.14352/59731©Johns Hopkins Univ Press. Research supported in part by an NSERC Grant. Research supported in part by NSF Grant DMS 89-01600.engjournal articlehttp://dx.doi.org/10.2307/2374757http://www.jstor.org/http://www.math.umn.edu/~olver/q_/lado2.pdfopen access51-73PhysicsMultidisciplinaryMathematicalFísica-Modelos matemáticosFísica matemática