History Of Middle Earth

I need some help from fans of the Tolkien books. I am looking to complete my US collection of The History Of Middle Earth but I am having problems finding some of the books in the editions that I have and I wonder if they were ever released in the format that I am looking for. If so, does anyone know the ISBNs or even better where to find it! At this point knowing that they exist would be a big help!

The format is hardcover and the series is the one with the solid color on the front. Here is a link to an example image.

http://images.overstock.com/f/102/31...0395680921.jpg

I am looking for the following:
The Return of the Shadow, The History of The Lord of the Rings, Part One: The History of Middle-earth (Vol. 6)
The Treason of Isengard, The History of The Lord of the Rings, Part Two: The History of Middle-earth (Vol. 7)
The War of the Ring, The History of The Lord of the Rings, Part Three: The History of Middle-earth (Vol. 8)
Sauron Defeated: The End of the Third Age, The History of The Lord of the Rings, Part Four: The History of Middle-earth (Vol. 9)


Thanks to everyone in advance.

Kirk