Tips:
If all remaining cells border a cell of another group, then it is the same as the one given cell. Example: the number 3 in group P => group N
If all possible cells for a number border a cell of another group, then you can eliminate.
Double pair: eliminate from other cells.
Example 3 cells remaining; cells 1 and 2 can not have both numbers A and B, so 3rd number C must be in one of those 2 cells; eliminate from 3rd cell.