We give some conditions as to when a (finite) direct sum of NCS modules (if no non-zero complement submodule is small) is again NCS, and also provide various conditions to be sufficient for a submodule of an NCS module to be NCS. Some comparisons between QF-rings, GP-injective rings, AGP-rings and NCS rings are investigated.
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Karabacak et al. (2020) studied this question.
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