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

The 4 elements in each group of this type of puzzle are: A, B, C, and D.

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

Each row is a group numbered as shown in this Sudoku-4-ABCD figure.

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

Each column is a group numbered as shown in this Sudoku-4-ABCD figure.

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

Each 2x2 square is a group numbered as shown in this Sudoku-4-ABCD figure.

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