@article{MM2_1976__18_154379,
     author = {Georg Stamou},
     title = {\"Uber die isotropen {Strahlensysteme.}},
     journal = {Manuscripta mathematica},
     pages = {15--24},
     publisher = {mathdoc},
     volume = {18},
     year = {1976},
     zbl = {0325.53010},
     url = {http://geodesic.mathdoc.fr/item/MM2_1976__18_154379/}
}