"Realistic planet in Blender" "How to make a realistic planet in Blender" (2004)
This is quite outdated, do to the fact that it has been made in 2004 (maybe even earlier, actually) with Blender version 2.30.
By the way, the idea behind still works; besides the fact that several things can be made in a different way now (for example by node materials), I think that the "three domes" technique is still a very good one to layer clouds on the surface.