Lee, Lung-FeiChesher, Andrew2009-12-022009-12-021984-01Lee, L. and Chesher, A., (1984), "Specification Testing when Score Test Statistics are Identically Zero: The Extremum Test", Discussion Paper No. 197, Center for Economic Research, Department of Economics, University of Minnesota.https://hdl.handle.net/11299/55368en-USWorking Paper