Model for the <issue-part> element.
A publisher may split an issue into two or more separately bound or separately issued parts. This element holds the identifiers (titles, part numbers, etc.) for those publishing components.
<!ENTITY % issue-part-elements "%just-rendition;" >
| bold | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | strike | underline | underline-start | underline-end | named-content | styled-content | sub | sup