Content Model

<!ENTITY % book-meta-model  
                        "(book-id*, subj-group*, book-title-group?,
                          (%contrib-group.class; |
                           %aff-alternatives.class; | %x.class;)*, 
                          author-notes?, pub-date*,
                          book-volume-number?, book-volume-id*, 
                          issn*, issn-l?, isbn*, 
                          publisher*, edition*,
                          supplementary-material*, 
                          pub-history*, 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

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