Table: document_format_info
Columns: language
creator
first_public_release_date
editor
viewer

Question: Which viewers have the language of troff (typesetter runoff) , groff (gnu runoff)?
SQL: SELECT "viewer" FROM document_format_info WHERE "language" = 'troff (typesetter runoff) , groff (GNU runoff)'

Question: Who is the creator when the view happens to gddm, afp viewer?
SQL: SELECT "creator" FROM document_format_info WHERE "viewer" = 'GDDM, AFP viewer'