And it's proven that proof-of-work doesn't work to stop spam https://www.semanticscholar.org/paper/%E2%80%9C-Proof-of-Work-%E2%80%9D-Proves-Not-to-Work-version

And it's proven that proof-of-work doesn't work to stop spam https://www.semanticscholar.org/paper/%E2%80%9C-Proof-of-Work-%E2%80%9D-Proves-Not-to-Work-version-0-.-2-Laurie-Clayton/7a58abc92dbe41c9e5b3c7b0a358ab9096880f25 https://www.semanticscholar.org/paper/%E2%80%9C-Proof-of-Wor...