Notes on type-2 triangular norms and their residual operators

•The flaws in type-2 triangular norms and their residual operators [14] are presented with counterexamples.•We provide the correct versions of incorrect conclusions in [14].•We list a table summarizing the incorrect conclusions and the corresponding corrected conclusions.

Li recently investigated type-2 triangular norms and their residual operators. In this paper, the flaws in calculations of T-extension operations of t-(co)norms and their residual operations are presented with counterexamples. Moreover, incorrect conclusions are corrected.