Injective modules -- Essential extensions and the injective hull -- Quasi-Injective modules -- Radical and semiprimitivity in rings -- The endomorphism ring of a quasi-injective module -- Noetherian, artinian, and semisimple modules and rings -- Rational extensions and lattices of closed submodules -- Maximal quotient rings -- Semiprime rings with maximum condition -- Nil and singular ideals under maximum conditions -- Structure of noetherian prime rings -- Maximal quotient rings -- Quotient rings and direct products of full linear rings -- Johnson rings -- Open problems