Αυθεντικό κείμενο - Αγγλικά - Another more abstract method, if a column / row /...

Another more abstract method, if a column / row / block has say two values which both only have two allowed possible squares, and these two squares are the same for both values then this pair of values must be in these two squares. All other values therefore can not be placed in these squares (if any others exist). The above is repeated for sets of three, four and five values too.