. Author manuscript; available in PMC: 2019 Aug 28.
Published in final edited form as: Soc Sci (Basel). 2019 Apr 20;8(4):127. doi: 10.3390/socsci8040127
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Figure 1.
Article selection flow chart.