https://www.google.co.uk/url?sa=t&source=web&rct=j&url=https://bitcoin.org/bitcoin.pdf&ved=2ahUKEwj0v6OC6bDeAhXolYsKHQ1wCBEQFjAAegQIBBAB&usg=AOvVaw05-4mYD7EyyKjwcHh8i0Vw
