They consider it a kind of money demand for an open economy . their analytical method is similar - - establishing a model including money demand function with a series of restrictions ; then solving the equation to get the optimal quantity of money demand 无论是货币模型,还是全球模型,都是在一系列约束条件下,建立一套带有货币需求函数的模型,并通过求得最优解来确定本外币的最适度需求量。