BITS 0.2
( label?, title*, subtitle*, ( contrib-group | 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 | abstract | trans-abstract )*, ( ext-link |
nav-pointer | nav-pointer-group )?, ( toc-entry )* )
BITS 1.0
( label?, title*, subtitle*, ( contrib-group | address | alternatives | answer | answer-set
| array | boxed-text | chem-struct-wrap | code | fig | fig-group | graphic | media
| preformat | question | question-wrap | 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 | abstract | trans-abstract )*, ( ext-link | nav-pointer | nav-pointer-group )?,
( toc-entry )* )
BITS 2.0
( label?, title*, subtitle*, ( contrib-group | address | alternatives | answer | answer-set
| array | boxed-text | chem-struct-wrap | code | explanation | fig | fig-group | graphic
| media | name-address-wrap | preformat | question | question-wrap | question-wrap-group
| 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 | abstract | trans-abstract )*,
( ext-link | nav-pointer | nav-pointer-group )?, ( toc-entry )* )
BITS 2.1
NO CHANGE IN CONTENT MODEL