A famous problem of economic theory, the conditions under which money (which is intrinsically worthless) can have a positive value in a general equilibrium, is called "Hahn's problem" after him.
著名的经济理论问题：货币（本质上是毫无价值的）在何种条件下在一般均衡中具有正的价值，后来被称为“哈恩难题”。