1. Ask about geth: snapshot acceleration. https://blog.ethereum.org/2020/07/17/ask-about-geth-snapshot-acceleration/
2. Bitcoin blockchain data torrent. https://bitcointalk.org/index.php?topic=145386.0
3. Bitcoin core client. https://bitcoin.org/en/bitcoin-core/
4. Bitcoin wiki - clients. https://en.bitcoin.it/wiki/Clients
5. Bitcoin wiki - scalability. https://en.bitcoin.it/wiki/Scalability#Simplified_payment_verification