Boaz Patt-Shamir Yiannis Tsiounis Yair Frankel Exact Analysis of Exact Change: The <i>k</i>-Payment Problem. 436-453 2000 13 SIAM J. Discrete Math. 4 http://epubs.siam.org/sam-bin/dbq/article/31811 db/journals/siamdm/siamdm13.html#Patt-ShamirTF00