BITS 0.2
( label?, title?, subtitle*, alt-title*, ( 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 )*, ( app | ref-list )* )
BITS 1.0
( label?, title?, subtitle*, alt-title*, ( abstract )*, ( kwd-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 )*, ( app | ref-list )* )
BITS 2.0
( label?, title?, subtitle*, alt-title*, ( abstract )*, ( kwd-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 )*, ( app | ref-list )* )
BITS 2.1
( ( object-id )*, label?, title?, subtitle*, alt-title*, ( abstract )*, ( kwd-group
)*, ( subj-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 )*, ( app | ref-list )* )