Abstract In this comment, we give four counterexamples to show that Conclusion 1, Conclusion 2, Theorem 1 and Theorem 2 of a recent paper [1] are incorrect. Click to show full abstract
Abstract In this comment, we give four counterexamples to show that Conclusion 1, Conclusion 2, Theorem 1 and Theorem 2 of a recent paper [1] are incorrect.
               
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