The element br is defined in module text. It belongs to group format.
Content model EMPTY
The br element forces a line break within a part of text.
It does not divide paragraphs (use p instead).
These elements contain br:
address, articletitle, author, caption, dean, degree, editor, em, foreign, freehead, glossref, head, indexref, keyword, legend, line, link, major, note, organization, p, pre, publisher, q, school, serialtitle, speaker, stage, strong, sub, submission, sup, term, title, tt, u, worktitle.