The ambassador of Otho was provoked by the Greek excuses,
cum Christophori filiam Petrus Bulgarorum Vasileus conjugem duceret, Symphona, id est consonantia scripto juramento firmata sunt, ut omnium gentium Apostolis, id est nunciis, penes nos Bulgarorum Apostoli praeponantur, 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.