2
An element $x$ of an algebraic ring $S$ is said to be right quasiregular if there exists another element $y\in S$ such that $x\circ y=x+y+xy=0$.
DEFINITION- A topological ring is said to be a $D_r$ - ring if its right quasiregular (r.q.r.) elements form a d-open set (union of open $F_{\s...