Complex sentence: He held synods in northern Europe: at Paris, Rheims, and Trier in 1147 and 1149 which were devoted to the reform of clerical life; he also considered and approved the works of Hildegard of Bingen.
Split into simpler sentences: He held synods in northern Europe, at Paris, Rheims, and Trier in 1147 and 1149 which were devoted to the reform of clerical life. He also considered and approved the works of Hildegard of Bingen.