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.
Quite a good dictionary for a Tai language (Tai-alect, muhaha!). The phonetics of it seem to be well described in the beginning and so is the writing system. The lemmata are sorted in the traditional Tai script way, but IPA is always given. The tones are numbered but explained on the beginning. I bought this book only because it does have an index in the end, from Chinese to Tai Lüe, so yes, actually it's bidirectional. :)