Official Website: http://zkoracle.network/
The references involved in this paper are as follows:
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.
Vallery Mou, Blockchain Oracles Explained, in Binance Academy, 2020
Julien Thevenard, "Decentralised Oracles: a comprehensive overview", in Medium, 2019