[17] park. information flows between non-deliverable forward (ndf ) and spot markets：evidence from korean currency [j]. pacific-basin finance journal，XX，9:363-377
[18] roberta. michael f，exchange rate regimes in an increasingly integrated world [j]，economy，XX，34:109-132
[19] prasad，e. ye. l_ the renminbi\'s role in the global monetary system[r], global economy and development at brookings,XX (2) : 169-185
[20] nelson c r, sigel a f. parsimonious modeling of yield curve [j]. journal of business, 1987，60:473- 489.