The ambassador of Otho was provoked by the Greek excuses,
cum Christophori filiam Petrus Bulgarorum
Vasileus conjugem duceret, Symphona, idest consonantia
scripto juramento firmata sunt, ut omnium gentium Apostolis,
idest nunciis, penes nos Bulgarorum Apostoli præponantur,
honorentur, diligantur (Liutprand in Legatione, p. 482.).
See the Ceremoniale of Constantine Porphyrogenitus, tom. i. p. 82, tom. ii. p. 429, 430, 434, 435, 443, 444, 446, 447, with the annotations of Reiske.