A more difficult example

First the obvious things:

Next look at row 8:

On row 4 digit 5 must be in the middle box.

The digits 1,4,5 in column 5 must be in the positions a,b,c, and nothing else is in these positions.

Now the 2 in the top row is determined.

That was the end of the work, all the rest is straightforward. (A 3 and 4 in row 2, a 5 and 1 in column 5, ...)