unnumbered" id="references">References<a class="anchor" aria-label="anchor" href="#references"></a>
</h2>
<div id="refs" class="references csl-bib-body hanging-indent">
<div id="ref-Barton1980" class="csl-entry">
Barton, J., C. Bain, C. H. Hennekens, B. Rosner, C. Belanger, A. Roth,
and F. E. Speizer. 1980. <span>“Characteristics of Respondents and
Non-Respondents to a Mailed Questionnaire.”</span> <em>American Journal
of Public Health</em> 70 (8): 823–25. <a href="https://pubmed.ncbi.nlm.nih.gov/7416