@article{IM_1977__40_142480,
     author = {Michael Walker},
     title = {On the {Structure} of {Finite} {Collineation} {Groups} {Containing} {Symmetries} of {Generalized} {Quadrangles.}},
     journal = {Inventiones mathematicae},
     pages = {245--266},
     publisher = {mathdoc},
     volume = {40},
     year = {1977},
     zbl = {0367.05017},
     url = {http://geodesic.mathdoc.fr/item/IM_1977__40_142480/}
}