Among Gabriel's identifiable sources are the 73 forged canons attributed to Marutha of Maypherqaṭ, the Syro-Roman law book, the Synodicon Orientale, a letter of the Catholicos Timothy I and a letter of the Catholicos Ishoʿ bar Nun.[2] He also used the legal writings of East Syriac scholars like Ishoʿbokht, Shemʿon of Rev Ardashir and ʿAbdishoʿ bar Bahrīz.[1]