And London's Transport Authority has promoted the Oyster card, a magnetic payment system that keeps track of where people have been and when.

VOA: standard.2010.04.01

If people start demanding payment on their notes then they will destroy the system.

如果人们开始要求纸币价值的兑现,他们将摧毁这个系统。

耶鲁公开课 - 金融市场课程节选

If people start demanding payment on their notes then they will destroy the system.

如果人们开始要求纸币价值的兑现,他们将摧毁这个系统。

耶鲁公开课 - 金融市场课程节选