https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef19045en.pdf
http://science.sciencemag.org/content/362/6412/287
http://www.ilo.org/wcmsp5/groups/public/—dgreports/—dcomm/—publ/documents/publication/wcms_604882.pdf
https://ecfsapi.fcc.gov/file/109303096909269/Sage%20&%20Carpenter,%202009.pdf