Complex sentence: The Miami Triad is a group of three fraternities founded at Miami University in Oxford, Ohio in the 19th century, which include Beta Theta Pi (1839), Phi Delta Theta (1848), and Sigma Chi (1855).
Split into simpler sentences: The Miami Triad is a group of three fraternities that were founded at Miami University in Oxford, Ohio in the 19th century. These fraternities, in the order they were founded, are Beta Theta Pi (1839), Phi Delta Theta (1848), and Sigma Chi (1855).