https://academic.oup.com/pnasnexus/article/4/3/pgaf071/8052021
Authors. Schneider, C. R. et al
Venue. PNAS Nexus 4(3)
How the Institute flags it
established 5 times frontier 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.