"The Apocalypse of Zephaniah (or Apocalypse of Sophonias) is an ancient pseudepigraphic text (one whose claimed authorship is unfounded) attributed to the Biblical Zephaniah and so associated with the Old Testament, but not regarded as scripture by Jews or any Christian group. It was rediscovered and published at the end of 19th century. The canonical Book of Zephaniah has much mystical and apocalyptic imagery, and this apocalyptic-style text deals with a similar subject." -- Wikipedia
Books can be attributed to "Anonymous" for several reasons:
* They are officially published under that name * They are traditional stories not attributed to a specific author * They are religious texts not generally attributed to a specific author
Books whose authorship is merely uncertain should be attributed to Unknown.