In in the second paragraph of Casper the Friendly Finality Gadget there is a double use the word 'and' -
There are two major schools of thought in PoS design. The first, chain-based proof of stake[1, 2], mimics proof of work mechanics and features a chain of blocks and and simulates mining by pseudorandomly assigning the right to create new blocks to stakeholders. This includes Peercoin[3], Blackcoin[4], and Iddo Bentov’s work[5].
In in the second paragraph of Casper the Friendly Finality Gadget there is a double use the word 'and' -