小弟不才，看xtabond2只有英文资料，没怎么看懂。。。由于想要看harsen统计量，所以只能用xtabond2了，想问一下这两行差分GMM和系统GMM的命令转换成xtabond2该怎么写呢？谢谢啦！

xtabond RD_density  v25 size capex year2 year4 year5 year6 year7, lags(1) maxldep(3) endogenous(LRD2, lag(0,2)) endogenous(wc, lag(1,2)) endogenous(CF, lag(1,.)) endogenous(debt, lag(1,.))  endogenous(equity, lag(1,.)) twostep

xtabond RD_density  v25 size capex year2 year4 year5 year6 year7, lags(1) maxldep(3) endogenous(LRD2, lag(0,2)) endogenous(wc, lag(1,2)) endogenous(CF, lag(1,.)) endogenous(debt, lag(1,.))  endogenous(equity, lag(1,.)) twostep vce(robust)

xtdpdsys RD_density  v25 size capex year2 year4 year5 year6 year7, lags(1) maxldep(3) endogenous(LRD2, lag(0,2)) endogenous(wc, lag(1,2)) endogenous(CF, lag(1,.)) endogenous(debt, lag(1,.))  endogenous(equity, lag(1,.)) twostep vce(robust)

xtdpdsys RD_density  v25 size capex year2 year4 year5 year6 year7, lags(1) maxldep(3) endogenous(LRD2, lag(0,2)) endogenous(wc, lag(1,2)) endogenous(CF, lag(1,.)) endogenous(debt, lag(1,.))  endogenous(equity, lag(1,.)) twostep