Let be a ring. A nonempty subset of is a subring of if is closed under negatives, addition, and multiplication. We determine the rings for which every subring of has a multiplicative identity (which need not be the identity of ).
"Rings whose subrings have an identity." Involve 13 (5) 823 - 828, 2020. https://doi.org/10.2140/involve.2020.13.823