libname pwl 'c:\empirical methods class\returns';
filename pwld 'c:\empirical methods class\returns';

data test1;
 infile pwld(gmmtest.txt) firstobs=2 missover;
 input aa;
aa2=aa*aa;
aa4=aa*aa*aa*aa;
proc means;
run;

proc model data=test1;
instruments nu;
parms nu;
eq.one=aa2-(nu/(nu-2));
eq.two=aa4-3*nu*nu/((nu-4)*(nu-2));
fit one two start=(nu=9.0) /gmm ;
run;