Intended as a pedagogical aid for attendees of his lectures, Hegel revised and extended the Encyclopedia over more than a decade, but stressed its role as a "textbook" in need of elucidation through oral commentary.[2] The 1830 text is widely available in various English translations[3] with copious additions (Zusätze) added posthumously by Hegel's students, deriving from their lecture notes. These additions expand on the text with examples and illustrations, and while scholars do not take the Zusätze to be verbatim transcription of Hegel's lectures, their more informal and non-technical style make them good stand-ins for the "necessary oral commentary".