Elements that may be used inside elements that are really expected to be #PCDATA and not to contain any of these things.
This Parameter Entity is even simpler than Simple Phrase-Level Textual Elements. Note that there is no math, and there are no links. This Parameter Entity is for modeling elements that an authoring DTD could restrict to merely #PCDATA, but an archival and interchange DTD dare not, since it needs to be able to handle the less mainstream cases.
<!ENTITY % simple-text "%emphasis.class; | %inline-display.class; | %phrase.class; | %subsup.class;" >