Logic Masters Deutschland e.V.

Standard Sudoku rules are in effect, i.e., each row, column, and 3x3 box must contain one each of the digits 1-9.

The circled digits are Quadruples, meaning that the four cells surrounding the circle must contain the given digit or digits, albeit in any order or position (these digits may also repeat as long as they don't contravene sudoku rules or prohibit the placement of other required digits in the quadruple.

A black dot indicates a Quad Sum, which means that one of the 4 surrounding cells contains the sum of the other three. Here, too, digits may repeat.

Finally, R4C9 is greater than R5C9.

F-puzzles link.

SudokuPad link.