- The Skull's chronological first appearance, in Judomaster #92, was actually published after his debut appearance, which takes place much later.
- This version of Rudolf Wolk (Earth-Four), including all history and corresponding appearances, was initially erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. However the ending of Convergence retroactively prevented that collapse, saving all the alternate realities, though in an "evolved" form. Even though versions of the character may have since appeared, this information does not apply to those versions.
- 3 Appearances of Rudolf Wolk (Earth-Four)
- 1 Images featuring Rudolf Wolk (Earth-Four)
- Quotations by or about Rudolf Wolk (Earth-Four)
- Character Gallery: Rudolf Wolk (Earth-Four)