Saying that some students use it as a textbook does not really tell us much. The reason I asked for a textbook or a paper in a reputable, refereed journal such as Nature or Lancet is that there is peer review, any material written is judged by the peers before it is published (in journals).
If a university used a book as a textbook, that tells me that a team of experts at the university has looked over the book carefully and agrees with pretty much everything the book says. There are some standards involved there.
Anybody can write a book, that means nothing. And if some students use that as a textbook, again, that doesn’t mean much. A student may like parts of the book and not other parts; he may simply ignore the parts he doesn’t agree with.
That does not happen with a textbook adopted by the university or a paper published in a reputable journal.
That is why I asked for a textbook, not a book which is used by some students as a textbook. There is a big difference.
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And if it is being used as a textbook by a university then one must look at calibre of the university. It is Harvard or Oral Roberts University?