SubSup
A calculation may require both sub script and super script elements. The <subsup> element takes care of these calculations. The <subsup> tag contains three elements: the main, the subscript, and the superscript elements. Each of these items may be a row if needed, as long as three elements are correctly contained within the tags. For example:
<math><msubsup><mi>X</mi><mrow><mn>1</mn><mn>2</mn></mrow><mrow><mn>3</mn><mn>4</mn></mrow></msubsup></math>
or
in the above example, the calculation was made up of two row elements and the main element. If only a single element was needed in either the superscript or subscript, then a a single row would have been required instead.
