De Ceremoniis
Either in 945 or 957, the ruling regent, Olga of Kiev, visited Constantinople with a certain priest, Gregory. Her reception at the imperial court is described in "De Ceremoniis". According to legends, Byzantine Emperor Constantine VII fell in love with Olga; however, she found a way to refuse him by tricking him to become her godfather. When she was baptized, she said it was inappropriate for a godfather to marry his goddaughter.