Let's face it. Deep research and study of anything, history or religion, or politics, or anythng - is not something that the Watchtower Society has been known for since Russell. I've seen many examples of items that are clearly plagiarized because of word sequencing or the use of an uncommon phrase only seen by one other author.
By all means they can quote from other books, studies, and speeches. What would it hurt if they had simply stated that "Frank S. Dobbins, in his book, 'Story of the World's Worship' (1904) wrote..."
But you see, the Watchtower doesn't really believe in copyright, nor do they understand "fair use" of another published work. They're the first ones to issue a DMA complaint against somebody for copying their work - even when it clearly falls under "fair use," but they pull quotes all the time and pass it off as their original work.
Let's face it: The Watchtower - The Proud Home of the World's Greatest......Hypocrites!!!
JV