Mixing mixed-mode designs in a national health interview survey: a pilot study to assess the impact on the self-administered questionnaire non-response., Braekman, Elise, Drieskens Sabine, Charafeddine Rana, Demarest Stefaan, Berete Finaba, Gisle Lydia, Tafforeau Jean, Van der Heyden Johan, and Van Hal Guido , BMC Med Res Methodol, 2019 Nov 21, Volume 19, Issue 1:212, (2019)