@article{AFM_1998_23_2_a10,
     author = {Kurt Strebel},
     title = {Point shift differentials and extremal quasiconformal mappings},
     journal = {Annales Fennici Mathematici},
     pages = {475--494},
     publisher = {mathdoc},
     volume = {23},
     number = {2},
     year = {1998},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AFM_1998_23_2_a10/}
}