@article{CMH_1995__70_3_140379,
     author = {J.M. Anderson and A. Hinkkanen},
     title = {Quadrilaterals and extremal quasiconformal extensions.},
     journal = {Commentarii mathematici Helvetici},
     pages = {455--474},
     publisher = {mathdoc},
     volume = {70},
     number = {3},
     year = {1995},
     zbl = {0839.30017},
     url = {http://geodesic.mathdoc.fr/item/CMH_1995__70_3_140379/}
}