Complex sentence: The three books of his "Commentarii", written in polished Latin, are an important source of information for the history of his cardinalate; they were edited at Rome in 1791 by Marotti.
Split into simpler sentences: The three books of his "Commentarii", written in polished Latin, are an important source of information for the history of his cardinalate. His "Commentarii" were edited at Rome in 1791 by Marotti.