2Mandelbaum M. Flexibility in Decision Making: an Ex- ploration and Unification [ D ]. Toronto: University of Toronto, 1978.
3Carlos O C, Marques R C. Flexible contracts to cope with uncertainty in public-private partnerships [ J ]. In- ternational Journal of Project Management, 2013,31 (3) : 473-483.
4Tadelis S. Public procurement design: lessons from the private sector [ J ]. International Journal of Industrial Organization, 2012, 30(3): 297-302.
5Levin J, Tadelis S. Contracting for government serv- ices: theory and evidence from US cities[J]. The Journal of Industrial Economics, 2010, 58 ( 3 ) : 507- 541.