@article{10_1017_S0017089500009447,
     author = {Leep, David B.},
     title = {Levels of division algebras},
     journal = {Glasgow mathematical journal},
     pages = {365--370},
     year = {1990},
     volume = {32},
     number = {3},
     doi = {10.1017/S0017089500009447},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500009447/}
}