@article{MZ_1977__155_172547,
     author = {Christoph Hering and Michael Walker},
     title = {Perspectivities in {Irreducible} {Collineation} {Groups} of {Projective} {Planes.} {I.}},
     journal = {Mathematische Zeitschrift},
     pages = {95--102},
     publisher = {mathdoc},
     volume = {155},
     year = {1977},
     zbl = {0367.50021},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__155_172547/}
}