How to enable (for example) Greek character entities in db5?

I'm trying to understand jpw to include some greek characters in a docbook v5 article but I fail to  understand how to enable the "Greek Letters Character Entities". 

The docbook guide says to specify the "Greek Letters Character Entities" (%isogrk1;) 

Q1: Where/how should this parameter be specified so I can reference the Greek character as entities in the text? 

If I read the XSL guide it says - and I quote:

>The DocBook DTD defines the character entities that make it easy to add

>special characters to your XML files. To enter a copyright symbol, for 

>example, it is easier to remember a name like © than the equivalent

>© Unicode entity. 

>

>Depending on the source for your DTD download, the files that

>define the character entity names may not be included. They are on the OASIS

>website under http://www.oasis-open.org/docbook/xmlcharent/index.shtml. Create

>a directory named ent in the directory where the DocBook DTD files are, and

>extract the entity files into ent. The DTD will find them in that location

>because it has references that look like "ent/iso-amsa.ent"."

But I still fail to understand how I can instruct (for example) "xsltproc" to recognize these additional entities. Even using the "raw" unicode fails since

xsltporc interprets that as an entity (i.e. ·) Since ENTITY is not really cosher in db5 the above explanation does not seem to apply anyway.

Can someone shine some light on the errors of my way here ?

/Johan