Kristensen, G. K., & Ravn, M. N. (2015). The voices heard and the voices silenced: Recruitment processes in qualitative interview studies.

This article describes sampling participants and its results for interview studies also with a focus on who was left out.

Kristensen, G. K., & Ravn, M. N. (2015). The voices heard and the voices silenced: Recruitment processes in qualitative interview studies. Qualitative Research, 15, 722–737.

Rapley, T. (2014). Sampling strategies.

This chapter has a focus on sampling in the light of data analysis.

Rapley, T. (2014). Sampling strategies. In U. Flick (Ed.), The SAGE handbook of qualitative data analysis (pp. 49–63). Sage. http://methods.sagepub.com/book/the-sage-handbook-of-qualitative-data-an...