1 Correction to: Brazilian Journal of Physics (2021) 51:1324–1332 https://doi.org/10.1007/s13538-021-00916-5

In the original article there is an important step missing in Eq. (16). The step is important because students tend to think that the support A of the test function is extended to infinity. In fact, this is not so and what we have is merely a calculation of an integral, viz. Following is the corrected equation:

$$\begin{aligned} \lim _{\alpha \rightarrow \infty } \int _{-A}^{A} dx \frac{\sin (\alpha x)}{x} = \lim _{\alpha \rightarrow \infty } \int _{-\alpha A}^{ \alpha A} dy \frac{\sin (y)}{y} = \pi \, , \end{aligned}$$
(16)

where in the last step we made the substitution \(\alpha x = y\).

In addition, following is the corrected Ref. 15:

15. S. De Vincenzo, C. Sánchez, Point interactions: boundary conditions or potentials with the Dirac delta function. Can. J. Phys. 88, 809 (2010).