Constantine VII Porphyrogenitus, b 17/18 May 905, d 9 Nov 959. Byzantine emperor and writer. During Constantine's reign there was strong interaction between the Kyivan and Byzantine states; for example, Prince Ihor led campaigns against Byzantium in 941 and 944 and signed a trade treaty with it in 944. Ihor’s widow, Princess Olha, visited Constantinople in 957 and was baptized there. The works written by Constantine (De administrando imperio) or edited by him (De thematibus, De ceremonis) contain much material on the history and geography of Kyivan Rus’.