Masaaki Harada Michio Ozeki Kenichiro Tanabe On the Covering Radius of Ternary Extremal Self-Dual Codes. 149-158 2004 33 Des. Codes Cryptography 2 http://dx.doi.org/10.1023/B:DESI.0000035468.86695.40 db/journals/dcc/dcc33.html#HaradaOT04