"Property that provides the human-readable label of the citation level (e.g. \"book\"@en, \"paragraph\"@en, or \"liber\"@lt, \"paragraphus\"@lt)" . "E.g. in: \"Verg. Aen. 1.10\", (book) \"1\" has reference type = 'book', (line) \"10\" has reference type = 'line'" . . .