To simulate the early Earth’s reducing atmosphere, which chemicals were used by Miller and Urey and in their famous Miller–Urey experiment?

In the Miller and Urey experiment in 1953, Stanley Miller and Harold Urey used methane (CH4), Ammonia (NH3), hydrogen (H2) gases and water vapour in an airtight apparatus and passed electrical discharges using electrodes, the found simple organic compounds and few amino acids such as glycine, alanine, and aspartic acid.