st: gmm2s option not allowed

["Suryadipta Roy" <sroy2138@gmail.com>]

Hi,

I am getting the following message when I am trying for the gmm2s option:

 use http://www.stata.com/data/jwooldridge/eacsap/mroz.dta

. ivreg2  lwage exper expersq ( educ= age kidslt6 kidsge6), gmm2s
option gmm2s not allowed
r(198);

Can someone please suggest a remedy to this?

Thanks,
Suryadipta.
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