Although we are using our own generators to produce original grids, we have imported several interesting sets of sudoku puzzles from various (mainly old) sources.
- http://magictour.free.fr/sudoku.htm lists several sets of hard sudokus that we imported in our database with the following source name: Hardest sudokus from magictour website. Importing the 4 datasets (87, 95, 234 and 1465 puzzles) resulted in a total of 1467 puzzles import in our database.
- From the same page, importing the files listed in "old lists with hard sudokus" led to 1768 additional puzzles imported in our database with source name Old list with hard sudokus from magictour.
The Enjoy Sudoku forum contains a huge number of puzzles:
- Fully symmetrical puzzles contains grids found in the following thread: http://forum.enjoysudoku.com/fully-symmetrical-puzzles-t3721.html
- Puzzles needing lots of locked candidates are taken from the following thread: http://forum.enjoysudoku.com/puzzles-needing-lots-of-locked-candidates-t5381.html
The following table lists all sources of our sudoku grids:
| Source | Puzzles |
|---|---|
| Old list with hard sudokus from magictour magictour.free.fr/sudoku.htm | 1 768 |
| Fully symmetrical puzzles forum.enjoysudoku.com/fully-symmetrical-puzzles-t372… | 1 690 |
| Hardest sudokus from magictour website magictour.free.fr/sudoku.htm | 1 467 |
| Gordon Royle 17 clues web.archive.org/web/20120722180233/http://mapleta.ma… | 439 |
| Sudokus with an original rare shape forum.enjoysudoku.com/sudokus-with-an-original-rare-… | 20 |
| Puzzles needing lots of locked candidates forum.enjoysudoku.com/puzzles-needing-lots-of-locked… | 12 |
| Nick70 Complete Sudoku Collection - Vol. 1 forum.enjoysudoku.com/complete-sudoku-collection-vol… | 6 |
| Dell Pencil Puzzles & Word Games #16, page 6, 1979-05 | 2 |
| Wikipedia Mathematics of Sudoku en.wikipedia.org/wiki/Mathematics_of_Sudoku | 1 |