Unprecedented extreme high-frequency radio variability in early-stage active galactic nuclei. - Järvelä, E; Savolainen, T; Berton, M; Lähteenmäki, A; Kiehlmann, S; Hovatta, T; Varglund, I; Readhead, A C S; Tornikoski, M; Max-Moerbeck, W; Reeves, R A; Suutarinen, S (Monthly Notices of the Royal Astronomical Society, 2024)