On zero subrings and periodic subrings.
Let be a module and be a class of modules in which is closed under isomorphisms and submodules. As a generalization of essential submodules Özcan in [8] defines a -essential submodule provided it has a non-zero intersection with any non-zero submodule in . We define and investigate -singular modules. We also introduce -extending and weakly -extending modules and mainly study weakly -extending modules. We give some characterizations of -co-H-rings by weakly -extending modules. Let ...
Left selfdistributive rings (i.e., ) which are semidirect sums of boolean rings and rings nilpotent of index at most 3 are studied.