Complex sentence: The high altar of the church was dedicated in 1072, but the monastery itself not until 1083: the foundation charter, dated 9 September 1083, is still preserved in the archives of the monastery.
Split into simpler sentences: The high altar of the church was dedicated in 1072, but the monastery itself not until 1083. The charter of foundation, dated 9 September 1083, is still preserved in the archives of the monastery.