. 2019 Jan 31;21(1):e11280. doi: 10.2196/11280
©Yinzi Jin, Mingxia Jing, Luyu Zhang, Suhang Song, Xiaochen Ma. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 31.01.2019.
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Figure 1.
Flowchart of sample selection from the CHARLS 2011.