ɪɾ ɪz bᵻlˈiːvd ðə pɹɪzˈɜːvd tˈɛksts ɪn ɹˈʌʃən tʃˈɜːtʃ slævˈɑːnɪk ɑːɹ tɹˈænskɹɪpts əvə lˈɔst ɚɹˈɪdʒɪnəl, ɹˈɪʔn̩ ɪn ˈoʊld bʌlɡˈɛɹiən dˈʊɹɹɪŋ ðə nˈaɪnθ ænd tˈɛnθ sˈɛntʃɚɹiz.
It is believed the preserved texts in Russian Church Slavonic are transcripts of a lost original, written in Old Bulgarian during the 9th and 10th centuries.