An entity name used as a default attribute value, for an attribute that is not specified in the attribute's start tag, must be a non-SGML data entity or a SUBDOC entity.
#0046 Markup Error
ISO 8879, 7.9.4.3
An entity name used as a default attribute value, for an attribute that is not specified in the attribute's start tag, must be a non-SGML data entity or a SUBDOC entity.