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.
I am an ovo-lacto Vegetarian, leaning towards no Ovo & Lacto in my food whenever possible... so this Cookbook was kind of a let down. Meat here, Poultry there and some Fish everywhere. Oh and most of the meat was Pork with Pork and some Pork on top of it. Even though we live in a Country with a good amount of Jews & Muslims.