@article{MAN_1973__201_162394,
     author = {William Casselman},
     title = {On {Some} {Results} of {Atkin} and {Lehner.}},
     journal = {Mathematische Annalen},
     pages = {301--314},
     publisher = {mathdoc},
     volume = {201},
     year = {1973},
     zbl = {0239.10015},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__201_162394/}
}