求助，stata跑面板数据 老是显示variable not found 但我在数据里确实有，求解！以下分别做了三次测试，前面两次是rd not found， 第二次普通面板也是rd not found, 第三次就能跑出结果，求解！

. xtabond2 rd l.rd  rd2 abse cgi cashflow1 cashholding1  stkissue dbtissue lnma
> rketbook growth size     i.indus accper2-accper10 ,gmm( rd ,lag(1  2))  gmm(
> abse ,lag(2 2)) gmm( l.cgi ,lag(1 2))  iv( cashholding1 cashflow1 stkissue  d
> .cgi  lnmarketbook growth  )robust
variable rd  not found


.  xtreg rd l.rd  rd2 abse cgi cashflow1 cashholding1  stkissue dbtissue lnma
variable rd  not found

xtreg rd dbtissue