3.8.4.3 Math Run
The Office Open XML math run element r ("[ISO/IEC-29500-1] §22.1.2.87; r") can contain:
A single Word 2003 XML rPr element
If the math run contains both an Office Open XML Math rPr element and a Word 2003 XML rPr element, the Office Open XML Math rPr element must occur first.
The Office Open XML math r element can also contain an unbounded number of elements from the following list:
Word 2003 XML fldChar element
Word 2003 XML noBreakHyphen element
Word 2003 XML pgNum element
Word 2003 XML pict element.
Note: Word is unable to recover the contents of the equationxml attribute if it includes a pict element.
Word 2003 XML softHyphen element
Word 2003 XML sym element
Word 2003 XML tab element
Those elements must occur after any rPr elements.