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[ag9018]

In reference to version 224734d7be7ff0c4a8adb3a206356ea122112f33

In laying out the three main sections of the textbook, the chapter numbering is one higher than it should be.

"(chapters 2-4)" should be "(chapters 1-3)" "(chapters 5-6)" should be "(chapters 4-5)" "(chapter 7)" should be "(chapter 6)"