What's wrong with this command ?
by COUNTR, sort xtabond2 ROA L.ROA GRTH MIX EFFIC SIZE SOLV RISK LIQUID LEVR INFL ECOGRTH, gmm(L.ROA GRTH MIX EFFIC SIZE SOLV RISK LIQUID LEVR INFL ECOGRTH,collapse) iv(GRTH MIX EFFIC SIZE SOLV RISK LIQUID LEVR INFL ECOGRTH) noleveleq nodiffsargan robust small

I want to sort my results by country and the error message I get is the following :
: required
r(100);