Add link to Claw image (non-user .ac.uk page that may last a long whi…

…le).

doc/edplot.md

@@ -243,7 +243,8 @@ For an interactive X Window, `-e 'set term x11' -l 'pause -1'` or the similar
 long-option version in `~/.config/edplot` also works.
 
 [^8]: There are others with even finer structure like "the comb" and so on.  The
-claw is so named because its *density* looks like a 5-fingered animal paw.
+claw is so named because its *density* looks like a 5-fingered animal paw.  An
+image is here: https://people.maths.bris.ac.uk/~wavethresh/help/claw.htm
 
 [^9]: This means both old & forecast numbers are [independent & identically
 distributed](https://en.wikipedia.org/wiki/Independent_and_identically_distributed_random_variables)