I am looking for an academic answer about the two terms "Decentralized" and "Distributed". the idea I have now is that decentralized systems (like blockchain) don't have a single point of control when in the distributed system we can control the whole system from a single point of the network.
Bitcoin is a decentralized distributed ledger, however, private blockchains are centralized distributed ledgers. Distributed system means 2 or more nodes work with each other in accordance to achieve the common goal. It does not tell you anything about central authority.
In private blockchains, the consensus is maintained internally by a consortium.