<source> element identifies a
resource from which the present topic is derived, either completely
or in part.
<source> element contains a description of the resource.
@keyref attributes can be used to reference a description of the resource. It is
implementation-dependent what it means when the element has both content and an
attribute-based reference to another resource.
This element is equivalent to the
in Dublin Core.
See appendix for information about this element in OASIS document type shells.
- Provides a reference to a resource from which the present resource is derived. See The href attribute for detailed information on supported values and processing implications.