The $authorSortKey is basically how the name is to be sorted, usually
it's "Lastname, First names" where the $author is the straight
"Firstnames Lastname"
An entity primarily responsible for making the resource.
Examples of a Creator include a person, an organization, or a service.
Typically, the name of a Creator should be used to indicate the entity.
Used for the dc:creator metadata parameter in the OPF file and the
docAuthor attribure in the NCX file.
The sort key is used for the opf:file-as attribute in dc:creator.