Concerning quadratic mappings acting from $\mathbb{R}^3$ to $\mathbb{R}^3$ in the above mentioned paper it is proved that the following are equivalent: (i) quadratic mapping $Q$ is surjective; (ii) surjectivity of $Q$ is stable, i.e. any “close” to $Q$ quadratic mapping is surjective; (iii) $Q(x)\neq 0$ for each $x\neq 0$, and for each regular value $y$ of the mapping $Q$ the set $Q^{−1}(y)$ consists of 2 or 6 points.