Before revision: Paper money or electronic money can be used, as long as it is backed by one of these commodities at a fixed exchange rate (in other words the paper is just a contract stipulating that the bearer can redeem the paper for a fixed measure (weight) of that particular commodity).
After revision: ,Paper money or electronic money can be used, as long as it is backed by one of these commodities at a fixed exchange rate (in other words the paper is just a contract stipulating that the bearer can redeem the paper for a fixed measure (weight) of that particular commodity).