Bignumber: https://github.com/MikeMcl/bignumber.js/blob/master/bignumber.min.js
Web3: https://github.com/ethereum/web3.js/blob/1.0/dist/web3.min.js
Keythereum: https://github.com/ethereumjs/keythereum/blob/master/dist/keythereum.min.js
Ethereumjs-tx: https://github.com/ethereumjs/browser-builds/blob/master/dist/ethereumjs-tx/ethereumjs-tx-1.3.3.min.js