The content model for the <etal> element
Some DTDs model the <etal> element as EMPTY, that is, the element has no content. Such an empty element is typically used as a place holder, for example, to mark the position where text such as “et al.” will be generated by a stylesheet. In this DTD, the element is usually used as an empty element, but the DTD also allows there to be content inside the <etal>, so the element is modeled with text content instead of as formally EMPTY and may contain text such as “Associates, co-workers, and colleagues”.
<!ENTITY % etal-model "(#PCDATA %etal-elements;)*" >