If you would like to use named entities in your DocBook file, you will need to add these lines inside the DOCTYPE declaration at the top of the file.
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [ <!ENTITY % isoEnts SYSTEM "http://www.nmt.edu/tcc/entities/isoents.ent"> %isoEnts; ] >
Assuming you build your DocBook document on a TCC host machine, your document will be able to use all the entities described here.
If you would prefer to work offline, download a copy of the
isoents.ent file (see Section 2, “Files for downloading”) to your
project directory and replace the entity declaration above
with this one:
<!ENTITY % isoEnts SYSTEM "isoents.ent">