Logical, defaulting to TRUE, indicating whether to clean the
data returned by the API. If TRUE, variables containing absolute paths to
the preprints web-page ("link_page") and PDF ("link_pdf") are generated
from the "server", "DOI", and "version" variables returned by the API. The
"title", "abstract" and "authors" variables are converted to title case.
Finally, the "type" and "server" variables are dropped.