Books can be attributed to "Unknown" when the author or editor (as applicable) is not known and cannot be discovered. If at all possible, list at least one actual author or editor for a book instead of using "Unknown".
Books whose authorship is purposefully withheld should be attributed instead to Anonymous.
Oh, oh it's March so fast it went February month?? Didn't it?? ... To go over this book it's a fast reading. It's a kind app for smart phones, this book has collected articles about the brain health and their put in one app, you just click the button down with the arrow and you go to the next article. The articles are short and fast reading! - What more awesome than that??