BITS 0.2
( ( 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 )*, ( book-part )* )
BITS 1.0
( ( 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 )*, ( sec )*, ( book-part | xi:include
)* )
BITS 2.0
( ( 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 )*, ( sec )*, ( book-part | xi:include )* )
BITS 2.1
NO CHANGE IN CONTENT MODEL