Something like this is the best I could find: https://craftofcoding.files.wordpress.com/2018/01/fortran_go... – the last page has a full listing with arrows to show the jumps.

I grew up with MSX-BASIC: https://github.com/plattysoft/Modern-MSX-BASIC-Game-Dev/blob... – GOSUB jumps to a specific line number (RETURN returns from where it jumped). Even a fairly simple and clean example like this can be rather difficult to follow.