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 love cooking, I love my dog - a cookbook for cooking dogfood seemed the obvious choice when I felt - again - like spending some money.
Needless to say, I have never cooked for my dog, due to time and the fact that I has a sensitive stomach and can't eat most of the things suggested in this book. Still love the idea though, and the recipes and their layout are very cute.