1. Bitstamp proof of reserves. https://www.bitstamp.net/s/documents/Bitstamp_proof_of_reserves_statement.pdf
2. Ethereum wiki (archive.org). https://web.archive.org/web/20190613115908if_/github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign
3. Kraken proof of reserves. https://www.kraken.com/en-us/proof-of-reserves-audit
4. Okex suspends withdrawals, says key holder not available due to cooperation with investigation. https://www.coindesk.com/okex-suspends-withdrawals
5. Provisions: Privacy-preserving proofs of solvency for bitcoin exchanges. Real World Crypto 2016. https://rwc.iacr.org/2016/Slides/Provisions