What am I missing here? I've applied all the rules I know in killer sudoku including both versions of the 45 rule. But regardless I'm still missing something. Probably something obvious, but
Killer Sudoku Puzzles Main Page and Killer Sudoku Cheat Sheet
Product Killer Sudoku — Rätselportal — Logic Masters Deutschland
The Logical World of Puzzles: Solving Killer Sudoku: (Unique Combinations)
Killer Sudoku Tips and Strategies
What is Killer Sudoku? How to Play Killer Sudoku - Mastering Sudoku
Killer Sudoku Rules - How to play Killer Sudoku
JSudoku - Advanced Techniques for Killer Sudoku
Killer Sudoku From Scratch - Puzzle Genius
Killer Sudoku Helper in Gleam on Exercism
What is Killer Sudoku? How to Play Killer Sudoku - Mastering Sudoku
Need help with this furiously annoying Killer Sudoku : r/sudoku