@article{MZ_1980__173_172980,
     author = {Zvonimir Janko and Tran van Trung},
     title = {On {Projective} {Planes} of {Order} {Twelve} and {Twenty.}},
     journal = {Mathematische Zeitschrift},
     pages = {199--202},
     publisher = {mathdoc},
     volume = {173},
     year = {1980},
     zbl = {0438.51009},
     url = {http://geodesic.mathdoc.fr/item/MZ_1980__173_172980/}
}