Buddeberg, K., G. Dutz, A. Grotlüschen, L. Heilmann, and C. Stammer. “Low Literacy in Germany: Results from the Second German Literacy Survey”. European Journal for Research on the Education and Learning of Adults, vol. 11, no. 1, Feb. 2020, pp. 127-43, doi:10.3384/rela.2000-7426.rela9147.