https://api.openalex.org/works/doi:10.1073/pnas.150237597
Authors. Swenson, W. A., Wilson, D. S. & Elias, R
Venue. Proceedings of the National Academy of Sciences 97:9110–9114
How the Institute flags it
frontier 2 times established 1 time
This source carries more than one flag across the corpus. That is not an inconsistency to resolve: the same work can be established evidence for one claim and frontier evidence for another, and the flag belongs to the use rather than to the source.