Martín, Unai, and Yolanda González-Rábago. “Qualitative Methodology to Focus the Quantitative Approach: The Experience of Cognitive Pretests Applied to the Health Survey of the Basque Country”. Empiria. Revista De metodología De Ciencias Sociales, no. 43, May 2019, pp. 137-58, doi:10.5944/empiria.43.2019.24302.