Jump to definition of entity under cursor
From Vim Tips Wiki
created 2004 · complexity basic · author Aron Stansvik · version 5.7
This is what I use when reading/editing DTDs that make use of entities heavily:
:map <Leader>e yiw ?<!ENTITY % <C-R>"<CR>
That will map
<Leader>e to search backwards for the definition of the entity under the cursor, then you can just CTRL-o back to where you were. Makes reading DTDs less painful.