Dan LeKander's 50th puzzle is difficult. You may learn the most when you tackle it yourself before looking at his solution!
Sudoku Puzzle Challenge–April 2016 > Thousand Islands Life
Thousand Islands Life Magazine, Puzzle #54 by Dan Lekander
Thousand Islands Life Magazine, Sudoku #48
Sudoku Puzzle # 27, July 2017 > Thousand Islands Life Magazine
Sudoku Puzzle Challenge–June 2016 > Thousand Islands Life Magazine
Thousand Islands Life, Sudoku Puzzle #70
Sudoku Puzzle Challenge–April 2016 > Thousand Islands Life
Thousand Islands Life Magazine, Sudoku #59
Sudoku Puzzle #31 > Thousand Islands Life Magazine > Thousand
Sudoku Puzzle Challenge, December 2016 > Thousand Islands Life
Thousand Islands Life Magazine, Sudoku Puzzle #60
Sudoku Puzzle Challenge, December 2016 > Thousand Islands Life
Thousand Islands Life, December Sudoku, #177, #178, #179 & #180