Documentary Hypothesis (i.e. who wrote the Pentateuch?!)

Following Claud's question about who wrote the first five books of the Bible (the Pentateuch), here are some links to websites about something called the 'Documentary Hypothesis'. This is a theory someone called Wellhausen first proposed, in which it is suggested that there were four main sources for the Pentateuch. This theory has slightly fallen out of favour/fashion recently but, so far as I'm aware, there aren't any other competing theories that are as well-developed as this one. This doesn't mean that this theory is right, just that it's the fullest suggestion that's out there!

• Wikipedia's entry on the documentary hypothesis (Wikipedia isn't always the most reliable source but can be good for getting an overview of a topic)
• A website about the documentary hypothesis (again this may not be that reliable but it is fairly clear)
• An article strongly criticising the documentary hypothesis
• A book about the making of the Pentateuch
• In this book, on page 27, there's a summary of the state of current scholarship regarding the documentary hypothesis