Aparecido Cardoso, J. A., F. Ishizu, J. de Lima, and J. Pinto. “Blockchain Based MFA Solution: The Use of Hydro Raindrop MFA for Information Security on WordPress Websites”. Brazilian Journal of Operations & Production Management, Vol. 16, no. 2, May 2019, pp. 281-93, doi:https://doi.org/10.14488/BJOPM.2019.v16.n2.a9.