@article{10_1017_S0017089500002329,
     author = {Piper, Fred},
     title = {On relative difference sets and projective planes},
     journal = {Glasgow mathematical journal},
     pages = {150--154},
     year = {1974},
     volume = {15},
     number = {2},
     doi = {10.1017/S0017089500002329},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500002329/}
}