Variant Sudoku: Not Your Average Number Puzzle

Help a beginner, why can't this 6 go in there? It's unique across the row, column and box, I don't get it. : r/sudoku

Thousand Islands Life, Sudoku Puzzle #42

All the different types of Sudoku Puzzle

The 10 Hardest Logic/Number Puzzles

Sudoku Variants: Conceptis Puzzles: 9781402741111: : Books

A sample 4 × 4 Sudoku puzzle with enumerated candidate sets. Circle

Sudoku Assistant -- Solving Techniques

Sudoku Variants as Playful Proof Practice

Sudoku Variants as Playful Proof Practice