** Detailed instructions for working a group puzzle of type 'Sudoku-4-UVWX' **

The 4 elements in each group of this type of puzzle are: **U**, **V**, **W**, and **X**.

Every group in the puzzle must contain *exactly* this set of elements.

In a Sudoku-4-UVWX puzzle, each row is a group numbered as shown in the figure above.

In a Sudoku-4-UVWX puzzle, each column is a group numbered as shown in the figure above.

In a Sudoku-4-UVWX puzzle, each 2x2 square is a group numbered as shown in the figure above.