Section 36.2 Notes and Commentary
The 
<commentary> element is designed primarily for the purpose of adding material to a document to make an enhanced version.  It is similar in many ways to a <paragraphs> in that it can be placed within any division and must be titled.  The main difference is that it is not displayed by default, so you must set a processing switch to enable its appearance.  In the project manifest inside your desired target, add the following.<stringparam key="commentary" value="yes"/>
Other distinctions are:
- Since it is elective, you need to be careful about cross-references to and from a<commentary>. It is highly likely that you will want to make cross-references within a<commentary>pointing to other portions of your text, and this is always a good idea. You will want to avoid making cross-references to a<commentary>from other parts of the text, with the exception of a cross-reference that originates within some<commentary>.
- Numbered items are prohibited within a<commentary>, such as a<figure>or a<theorem>. Doing so would disrupt consecutive numbering in different versions, with or without,<commentary>included. Numbered equations are not prohibited in the schema, but should definitely be avoided anyway.

