Official diagram of the WGS 84 Reference Frame.
Defense Mapping Agency
Section 1-5 PDF of the DMA TECHNICAL REPORT TR8350.2-b - (Second Printing, 1 December 1987) Supplement to DoD WGS 84 Technical Report Part 2 - Parameters, Formulas, and Graphics. here: <a rel="nofollow" class="external free" href="http://earth-info.nga.mil/GandG/publications/tr8350.2/TR8350.2-b/Sections%201-5.pdf">http://earth-info.nga.mil/GandG/publications/tr8350.2/TR8350.2-b/Sections%201-5.pdf</a>