I found this Sudoku X in a German magazine called "Sudoku Logisch Spezial" (Issue No. 14 from June 2008).
Some cells of the grid are restricted to even numbers. These are C7, C8, D3, E5, F2, G1, I2 and I7.
The difficulty is rated "easy"... *sigh*
After spending some hours I gave up, tried again some weeks later and so on - until today.
I remembered your web-site and wanted to be shown what I have overlooked and I the end it claimed "Run out of known strategies."
For you are interested in examples that can't be solved on this page I sent this to you. The SolutionCount-Button did not work! ("Not available just yet")
I don't know whether there is a solution derived from any strategies, maybe it is only a misprint, but the given one on the last pages of the magazine is this:
Apart from that I just can say that this homepage is a great benefit when stuck in a puzzle.
Thanks a lot.