The Crossref schema supports minimal face markup in order to avoid ambiguity in certain disciplines (e.g. Genetics, where the same text may be a gene (when italicized) or a protein (when not italicized).
Face markup that appears in the title, subtitle, original_language_title, and unstructured_citation elements should be retained when depositing metadata. Face markup in other elements (e.g. small caps in author names) must be dropped. Face markup support includes bold (b), italic (i), underline (u), over-line (ovl), superscript (sup), subscript (sub), small caps (scp), and typewriter text (tt).
Examples where inclusion of face markup is especially important include:
- Italic in titles for terms such as species names or genes
- Super and subscript in titles as part of chemical names (e.g. H20)
- Super and subscript in simple inline mathematics (e.g. x2 + y2 = z2)
The schema supports nested face markup (e.g. "This text is bold and italic"), which would be tagged as:
This text is <b><i>bold and italic</i></b>
Correspondingly, super and subscript may be nested for correct representation of xyz. This expression should be tagged as:
Crossref also supports MathML markup in title elements.