Hint:
The black King is obviously in a pretty tenuous position. If you have spent some time on this puzzle already, then you have probably found a couple ways in which white almost mates the King. So, if you have found a way in which white would have a forced mate except for one escape square, then why not find a way to cover that square and see if black has a way out?
That should pretty much give it to anyone that hasn't solved it yet. If you still really have hit the wall with this one, just message me, and I will send you the solution.
There is also the link that I provided previously. Although, I'm not sure if they ever got it right...
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