Published on in Vol 23, No 2 (2021): February
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/25108, first published
.
1 Center for Tobacco Control Research and Education, University of California, San Francisco, San Francisco, CA, United States
2 Department of Mathematics, University of California, Davis, Davis, CA, United States