Complex sentence: The Longmen Relics Care Agency established in 1953 under the Ministry of Culture and the Longmen Grottoes Research Institute established in 1990 under the People's Government of Luoyang City are responsible for the management of the heritage monuments.
Split into simpler sentences: The Longmen Relics Care Agency was established in 1953 under the Ministry of Culture. The Management and Conservation Office was renamed the Longmen Grottoes Research Institute in 1990; and the People's Government of Luoyang City became responsible for the management of the heritage monuments.