Martine Batchelor (2014). The Spirit of the Buddha. Yale University Press. p. 59. ISBN978-0-300-17500-4.; Quote: These five trades, O monks, should not be taken up by a lay follower: trading with weapons, trading in living beings, trading in meat, trading in intoxicants, trading in poison."
Paner, Henryk. "Nubian Rock Art." in Geoff Emberling, and Bruce Beyer Williams (eds). The Oxford Handbook of Ancient Nubia (2021); online edn, Oxford Academic,13 Jan. 2021, https://doi.org/10.1093/oxfordhb/9780190496272.013.51.