<source> element/style reference link

I noticed in Julian’s styles that he used the element to
include a link to the reference document he used to create the style.
Including such a link seems like a very good idea, but technically this
isn’t the purpose of the element in the Atom spec

If we want to stay in line with the Atom spec for these borrowed
elements, the element is probably more appropriate. (We may also
want to use for its actual purpose if, say, we aggregate styles
from other locations in the Zotero repository.) In Atom it looks like

is supposed to use the "href" attribute rather than node data, and for this purpose rel="via" might be best ("the source of the information provided in the containing element"), but at the moment the CSL schema doesn't allow attributes on . Do we want to change the schema to allow these attributes (and disallow node data)?

Yes. My intention was always that the content model for CSL metadata
be the same as Atom.