9. Uniquenessconstraint: J1=5 The green area (GHJ12) only contains the digits 2345. If 5 in J1 were to be removed, the uniqueness constraint would be violated J1 has to be 5 (Uniqueness idea by Siegbert in the str8ts.de forum.)
17. Weekly Extreme Str8ts Puzzle #13www.str8ts.com Solution by SlowThinker (Uniqueness idea by Siegbert) Note: There are other (maybe easier or more logical) ways to solve this puzzle.