@article{MZ_1974__138_172083,
     author = {E.F jr. Assmus and H.F. Mattson and M. Guza},
     title = {Self-Orthogonal {Steiner} {Systems} and {Projective} {Planes.}},
     journal = {Mathematische Zeitschrift},
     pages = {89--96},
     publisher = {mathdoc},
     volume = {138},
     year = {1974},
     zbl = {0273.50016},
     url = {http://geodesic.mathdoc.fr/item/MZ_1974__138_172083/}
}