“…Moreover, if such an idempotent exists, say e (f Se = 0, where f = 1 − e), then, for M := eSf , emf = m for every m ∈ M . This property on M and its consequences (see Lemma 2.5 below) play a crucial role in proving some interesting results (see, for instance, [3,11,13]). In [11,Example 3.13] and [13,Example 2.6], examples of trivial extension algebras A ⋉ M with the suitable idempotent of A without having a triangular matrix representation are given.…”