I am writing a thesis about blockchain and part of my writing is the history of blockchain, so far I found the first proposal was “How to Time-Stamp a Digital Document” in 1991 by Haber and Stornetta. Source: https://www.quora.com/What-is-the-history-of-blockchain-technology
The second proposal was by the unknown Satoshi Nakamoto, “Bitcoin: A Peer-to-Peer Electronic Cash System”.
So my question is there any other proposals before the Bitcoin implementation of blockchain?