H. Al-Breiki, M. H. U. Rehman, K. Salah and D. Svetinovic, “Trustworthy Blockchain Oracles: Review, Comparison, and Open Research Challenges,

H. Al-Breiki, M. H. U. Rehman, K. Salah and D. Svetinovic, “Trustworthy Blockchain Oracles: Review, Comparison, and Open Research Challenges,” in IEEE Access, vol. 8, pp. 85675–85685, 2020, doi:10.1109/ACCESS.2020.2992698.