I have today managed to solve the very hard puzzle below but only using trial and error. Can anyone advise pse as to whether there is a logical step that I missed from the position shown. I suspect that there is but I couldn't see it for looking.
Many thanks in advance.
Zeb
91* *73 4*6
*76 2** 51*
*** **1 7**
124 *35 6**
8*9 *** 3*1
**7 1** 24*
79* 3** 1**
**3 *17 9**
2*1 *9* 837