What is/are the first proposal(s) of blockchain or alternatives? 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?
In addition to "How to Time-Stamp a Digital Document", in 1992, Bayer, Haber and Stornetta incorporated Merkle trees to the design, which improved its efficiency by allowing several documents to be collected into one block in a book "Improving the Efficiency and Reliability of Digital Time-Stamping"