That’s a great question, Roslyn. I went back and looked at the chronological book list that I had created for that study, and it lists The Sword in the Tree before Viking Adventure. Yet somehow between that list and the final lesson-by-lesson list, those two titles were switched. Unfortunately, I didn’t leave a note to myself about why. So either it was a mistake or, more likely, it was done to try to fit complete books within each term rather than starting in one term and finishing in another.
Feel free to switch the order if you would prefer.