J. Castro <em>et al.</em>" Island of Operations: a digital educational resource with multiple representations for understanding the additive field", in <em>Companion Proceedings of the 9th Brazilian Congress on Computers in Education</em>, Online, 2020, pp. 108-115, doi: <a href="https://doi.org/10.5753/cbie.wcbie.2020.108">https://doi.org/10.5753/cbie.wcbie.2020.108</a>.