Complex sentence: Its mandate was enlarged by the 1977 Charter of the French Language, which also established two other organizations: the Commission of Toponymy and the "Conseil supérieur de la langue française" (Higher Council of the French Language).
Split into simpler sentences: Its mandate was enlarged by the 1977 Charter of the French Language. The Commission of Toponymy and the "Conseil supérieur de la langue française" (Higher Council of the French Language).