Salguero-Alcañiz, María P., and José R. Alameda-Bailén. “Independence of Basic Arithmetic Operations: Evidence from Cognitive Neuropsychology”. Anales De Psicología Annals of Psychology, vol. 29, no. 3, Oct. 2013, pp. 1006-12, doi:10.6018/analesps.29.3.175721.