This attribute holds the name of an entity. The declaration for that entity must involve an external reference to an image data file:

<!ENTITY MyBoat SYSTEM "MyBoat.gif" NDATA GIF>
...
... entityref="MyBoat" ...

This attribute provides an alternative mechanism to the fileref or filename attributes, so while all three attributes are optional, in practice one must be used and the alternative should then not be used.

Note that the name of the file (without its path) should also be stored in the filename attribute.

Defined in shared attribute group: "File Reference Attributes"

This attribute is not required. It contains a reference to a entity definition (the element is replaced by the entity content).

The DTD contains the following attribute definition (note that embedded links are to definitions within the DTD page of this guide):

                entityref                ENTITY  #IMPLIED