Complex sentence: Evelyn diary's record of that August 18,1649 event refers to the Duke of Monmouth, which was a non-existent title until February 14,1663, thus the accuracy of it has been seriously questioned by authors.
Split into simpler sentences: Evelyn diary's record of that August 18,1649 event refers to the Duke of Monmouth, which was a non-existent title until February 14,1663. Thus the accuracy of it has been seriously questioned by authors.