@article{10_4153_CJM_1996_023_6,
     author = {Allison, Bruce N. and Gao, Yun},
     title = {Central {Quotients} and {Coverings} of {Steinberg} {Unitary} {Lie} {Algebras}},
     journal = {Canadian journal of mathematics},
     pages = {449--482},
     year = {1996},
     volume = {48},
     number = {3},
     doi = {10.4153/CJM-1996-023-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1996-023-6/}
}