BITS 0.2
( collection-id*, subj-group*, title-group?, ( contrib-group | aff | aff-alternatives
| x )*, author-notes?, pub-history*, volume?, volume-id*, 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 )* )
BITS 1.0
( 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 )* )
BITS 2.0
NO CHANGE IN CONTENT MODEL
BITS 2.1
( collection-id*, subj-group*, title-group?, ( contrib-group | aff | aff-alternatives
| x )*, author-notes?, content-language*, pub-date*, 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 )* )