1. Big data universe.
http://www.csc.com/insights/flxwd/78931-big_data_universe_beginning_to_explode
. Accessed 2 Mar 2018
2. Closed, shared, open data.
https://theodi.org/blog/closed-shared-open-data-whats-in-a-name
. Accessed 5 Mar 2018
3. Data and services.
http://www.icsu-wds.org/services/data-portal
. Accessed 5 Mar 2018
4. Archives.
https://www.archives.gov/open
. Accessed 5 Mar 2018
5. DBPedia.
http://wiki.dbpedia.org/
. Accessed 5 Mar 2018