Let $R$ be an associative ring in which an identity element is not assumed. A right quotient ring of $R$ is an overring $S$ such that for each $a\in S$ there corresponds $r\in R$ such that $ar\in R$ and $ar\neq 0$
Is a MAXIMAL QUOTIENT RING for $R$ a ring $S$ maximal with respect to above property?
For a commutative unital ring, can we deduced that MAXIMAL QUOTIENT RING=$R_S$, where $S$ is the set of all non zero-divisors?
Is there any simple comprehensive references for maximal quotient rings?