Content Model

<!ENTITY % collection-meta-model   
                        "(collection-id*, subj-group*, title-group?, 
                          (%contrib-group.class; |
                          %aff-alternatives.class; | %x.class;)*, 
                          author-notes?, pub-history*, 
                          volume-in-collection*,
                          issn*, issn-l?, isbn*, 
                          publisher*, edition*, 
                          permissions?, self-uri*,
                          (%related-article.class;)*,
                          (%abstract.class;)*, trans-abstract*, 
                          (%kwd-group.class;)*,
                          funding-group*, conference*, counts?,
                          custom-meta-group*,
                          (%front-back.class;)* )"                   >

Expanded Content Model

(collection-id*, subj-group*, title-group?, (contrib-group | aff | aff-alternatives | x)*, author-notes?, pub-history*, volume-in-collection*, issn*, issn-l?, isbn*, publisher*, edition*, permissions?, self-uri*, (related-article | related-object)*, (abstract)*, trans-abstract*, (kwd-group)*, funding-group*, conference*, counts?, custom-meta-group*, (notes)* )