Abstracts may contain one or more paragraphs (as a typical abstract does) or titled sections, as is done in many physics articles. Unlike the default model in the base DTD Suite, this <abstract>; requires that all sections in the abstract start with titles.
<!ENTITY % abstract-model
"((%id.class;)*, %sec-opt-title-model; )" >((object-id)*, (sec-meta?, label?, title?, subtitle*, alt-title*, (address | alternatives | array | boxed-text | chem-struct-wrap | fig | fig-group | graphic | media | preformat | supplementary-material | table-wrap | table-wrap-group | disp-formula | disp-formula-group | def-list | list | tex-math | mml:math | p | related-article | related-object | ack | disp-quote | speech | statement | verse-group | x)*, (sec)*, (notes | fn-group | glossary | ref-list | sig-block)* ) )
BITS-bookcustom-models0.ent