1. Abrams L.S. (2010), Sampling ‘Hard to Reach’ Populations in Qualitative Research: The Case of Incarcerated Youth, “Qualitative Social Work”, 9(4), 536–550. http://dx.doi.org/10.1177/1473325010367821.
2. Anderson B., Blinder S. (2015), Who Counts as a Migrant? Definitions and their Consequences, Migration Observatory Briefing, COMPAS, University of Oxford, UK. https://migrationobservatory.ox.ac.uk/wp-content/uploads/2017/01/Briefing-Who-Counts-as-a-Migrant-Definitions-and-their-Consequences.pdf (data dostępu: 29.11.2019).
3. Atkinson R., Flint J. (2001), Accessing hidden and hard-to-reach populations: Snowball research strategies, “Social Research Update”, 33(1), 1–4.
4. Baltar F., Brunet I. (2012), Social research 2.0: virtual snowball sampling method using Facebook, “Internet Research”, 22(1), 57–74. http://dx.doi.org/10.1108/10662241211199960.
5. Bańko M. (2015), w Ukrainie czy na Ukrainie?. https://sjp.pwn.pl/poradnia/haslo/w-Ukrainie-czy-na-Ukrainie;16214.html (data dostępu: 28.11.2019).