sentences: "The earliest version of a Tropologion dedicated to the repertoire of Octoechos was created by Severus of Antioch, Paul of Edessa and John Psaltes between 512-518.The Tropologion was expanded upon by St. Cosmas of Maiuma († 773), Theodore the Studite († 826) and his brother Joseph of Thessalonica († 832), Theophanes the Branded (c. 775-845), the hegoumenai and hymnographers Kassia (810-865) and Theodosia, Thekla the Nun, Metrophanes of Smyrna († after 880), Paul, Metropolit of Amorium, and by the emperors Leo VI and Constantine VII (10th century) as well as numerous anonymous authors.