@article{MM2_1973__8_154131,
     author = {Ralph Hugh Francis Denniston},
     title = {Uniqueness of the {Inversive} {Plane} of {Order} 7.},
     journal = {Manuscripta mathematica},
     pages = {21--26},
     publisher = {mathdoc},
     volume = {8},
     year = {1973},
     zbl = {0251.05019},
     url = {http://geodesic.mathdoc.fr/item/MM2_1973__8_154131/}
}