@article{MZ_1973__132_171930,
     author = {James S.W. Wong and Anton Zettl},
     title = {On the {Limit} {Point} {Classification} of {Second} {Order} {Differential} {Equations.}},
     journal = {Mathematische Zeitschrift},
     pages = {297--304},
     publisher = {mathdoc},
     volume = {132},
     year = {1973},
     zbl = {0257.34030},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__132_171930/}
}