Consensus mechanisms "are crucial for a blockchain in order to function correctly. They make sure everyone uses the same blockchain" .
From Investopedia: A consensus mechanism is a fault-tolerant mechanism that is used in computer and blockchain systems to achieve the necessary agreement on a single data value or a single state of the network among distributed processes or multi-agent systems .
From KPMG: Consensus mechanism - A method of authenticating and validating a value or transaction on a Blockchain or a distributed ledger without the need to trust or rely on a central authority. Consensus mechanisms are central to the functioning of any blockchain or distributed ledger .
 "Different Blockchain Consensus Mechanisms", Hacker Noon [online]. Available: https://hackernoon.com/different-blockchain-consensus-mechanisms-d19ea6c3bcd6. Date accessed: 2019‑06‑07.
 Investopedia: "Consensus Mechanism (Cryptocurrency)" [online]. Available: https://www.investopedia.com/terms/c/consensus-mechanism-cryptocurrency.asp. Date accessed: 2019‑06‑07.
 KPMG: "Consensus - Immutable Agreement for the Internet of Value" [online]. Available: https://assets.kpmg/content/dam/kpmg/pdf/2016/06/kpmg-blockchain-consensus-mechanism.pdf. Date accessed: 2019‑06‑07.