Iliya Bouyukliev Markus Grassl Zlatko Varbanov New bounds for n4(<i>k, d</i>) and classification of some optimal codes over GF(4). 43-66 2004 281 Discrete Mathematics 1-3 http://dx.doi.org/10.1016/j.disc.2003.11.003 db/journals/dm/dm281.html#BouyuklievGV04