The relationship between money and credit is discussed in terms of network linkage. Fiat money is the only instrument with the universal recognition of its issuer. Near monies such as bank money and money substitutes such as gasoline credit cards can be classiﬁed in terms of their network links. This leads to a way of considering the velocity of money.
Shubik, Martin, "Money and the Monetization of Credit" (2001). Cowles Foundation Discussion Papers. 1605.