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. 2019 Aug 19;21(8):e14021. doi: 10.2196/14021

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©Lance Garrett Shaver, Ahmed Khawer, Yanqing Yi, Kris Aubrey-Bassler, Holly Etchegary, Barbara Roebothan, Shabnam Asghari, Peizhong Peter Wang. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 19.08.2019.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in the Journal of Medical Internet Research, is properly cited. The complete bibliographic information, a link to the original publication on http://www.jmir.org/, as well as this copyright and license information must be included.

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Details of the Facebook advertising and recruitment process. Note that the total estimated reach is lower than the sum of the number reached by individual advertisements, as some people were reached by multiple advertisements.