languageName: The language name as written in the source document in freeform text. This allows a locally accepted name to be found in addition to the standard encoded in Austlang for the nearest standard language name
publicationDate: Date the document first appeared (format YYYY-MM-DD). Use the closest date if the exact date is not known (https://schema.org/datePublished)
dateFreeText: When the document first appeared if the date is not known (can be free text, can be just a year)