Similar to citations, references to equations (<men> and <mrow> elements) will visually look like (4.2), where the type name is implied by the parentheses. Notice that you cannot cross-reference an <me> element (it has no number) or an <md> element (it is just a container, filled with <mrow> that you can target if you give them numbers). Consult Subsection 4.9.3 for details about controlling the numbering of equations within an <md> or <mdn> element.
