@article{NUMA_1979__32_132620,
     author = {G. Opfer},
     title = {New {Extremal} {Properties} for {Constructing} {Conformal} {Mappings.}},
     journal = {Numerische Mathematik},
     pages = {423--430},
     publisher = {mathdoc},
     volume = {32},
     year = {1979},
     zbl = {0432.30007},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1979__32_132620/}
}