XSLT 1.0 + EXSLT
If I (or, ahem, preferably someone else) was going to port my XSLT 2.0 version of CiteProc to 1.0, this is a hint of how to do it. So like the current version, use custom functions to do the heavy-lifting, and keep the templates as clean as possible. It’s really not possible to do without support for EXSLT though.
