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Levels 51 to 60
The level 51 through 60 tradeskill books are sold only in Maj'Dul, and all is not cut and dried. The only part about this that is simple is that you do not need to own the DoF expansion in order to scribe these books
Levels 60-69
The level 60-69 recipe books, introduced with the release of the Kingdom of Sky Expansion, splits out the recipe books once again into different locations based on your tradeskill profession.