Forming a MIME_TYPE Attribute list

["Marker, Mike" <Mike.Marker@FMR.com>]

Title: Forming a MIME_TYPE Attribute list

In the process of defining a DTD, I would like to create an attribute list containing the following values - text/html, application/pdf, image/tiff.

The following does not work:

<!ATTLIST MIME_TYPE value (text/html | application/pdf | image/tiff) "image/tiff">

due to the '/' characters.

Would anyone know of the appropriate way for me to setup this element?