Block (formerly Square) is building a system for bitcoin miners
Jack Dorsey's Block Looks to Disrupt Bitcoin Mining - Blockworks
Twitter CEO Jack Dorsey Has Set up His Own Bitcoin Node - CoinDesk
Jack Dorsey Says Bitcoin Changes Everything 'For the Better' - BNN
Jack Dorsey's payments company Block is building a system for
Block Is Building a Bitcoin Mining System, Jack Dorsey Says
Jack Dorsey's Block Announces Bitcoin Mining System, Building the
Alex Gladstein Interviews Square and Twitter CEO Jack Dorsey
Jack Dorsey is Hodling - CEO Insight