Ha Quy Nguyen Vivek K. Goyal Lav R. Varshney On concentric spherical codes and permutation codes with multiple initial codewords. 2038-2042 2009 ISIT http://doi.ieeecomputersociety.org/10.1109/ISIT.2009.5205511 conf/isit/2009 db/conf/isit/isit2009.html#NguyenGV09