====== Advanced Sudoku Techniques ======
===== Lesson 13  There is only one place it can go =====
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===== Lesson 14. Matching pairs advanced =====
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===== Lesson 15. 3 empty cells in a row within a block =====
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===== Lesson 16. The Walking stick =====
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===== Lesson 17. The Capital T =====
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===== Lesson 18. The amazing 3X3 =====
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===== Lesson 19. Advanced TMB LCR =====
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===== Lesson 20. The cleaver, Mallet Table, and the Diagonal cross  pattern =====
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===== Lesson 21. The Xwing plus scenarios =====
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===== Lesson 22. Review scenarios and the skyscraper pattern =====
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===== Lesson 23. Review. The swordfish pattern =====
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===== Lesson 24. When all else fails #1. Using a matching pair =====
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===== Lesson 25. When all else fails. #2. The underlined pair. =====
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