9J. E. Stiglits , Andrew, Weiss Credit Rationing in Markets with Imperfect Information[J] American Economic Review, Vol. 71,1981, P393-410.
10Allen. N. Berger , G. F. Udell Relationship lending and lines of Credit in Small Firm Finance [J] The Journal of Business , Vol. 68,No. 3 , 1995, P351 -381.