@article{AM2_1972__8_136304,
     author = {N.S. Mendelsohn and D.M. Johnson},
     title = {Extended {Triple} {Systems.}},
     journal = {Aequationes mathematicae},
     pages = {291--298},
     publisher = {mathdoc},
     volume = {8},
     year = {1972},
     zbl = {0256.20096},
     url = {http://geodesic.mathdoc.fr/item/AM2_1972__8_136304/}
}