DOCBOOK: Multiple Xref pointers from a single location

[Jay Shah <jayesh@skyscape.com>]

Xref can be used to reference one location from another. However, I would
like to be able to reference multiple destinations from a single "hot-spot"
location in the document. How can this be achieved? Here is an example:

Book content:

"The drug apoxilin is available from XYZ, Inc."

During rendering, when the user clicks "apoxilin", a pop up will display the
following three links, related to the drug:

adverse reactions
generics
dosage

When the user clicks on one of these links, the appropriate section is
displayed.

How can the book be encoded using the docbook sgml/xml tags so that the
rendering software can automatically do what we need, without any coding?

/Jay