@article{10_4064_ap_57_1_29_44,
     author = {John Ryan},
     title = {Generalized {Schwarzian} derivatives for generalized fractional linear transformations},
     journal = {Annales Polonici Mathematici},
     pages = {29--44},
     year = {1992},
     volume = {57},
     number = {1},
     doi = {10.4064/ap-57-1-29-44},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-57-1-29-44/}
}