Stability of strongly Gorenstein flat modules

A left $R$-module $M$ is called two-degree Ding projective if there exists an exact sequence $…\longrightarrow D_{1}\longrightarrow D_{0}\longrightarrow D_{-1}\longrightarrow D_{-2}\longrightarrow…$ofDingprojectiveleft$R$-modulessuchthat$M\cong\ker (D_{0}\longrightarrow D_{-1})$and$\Hom_{R} (-, F)$leavesthesequenceexactforanyflat(orGorensteinflat)left$R$-module$F$. In this paper, we show that the two-degree Ding projective modules are nothing more than the Ding projective modules.