Shared-optical-path VLBI frequency phase transfer from 86 to 258 GHz on an 8600km baseline: Demonstrated with the APEX and IRAM 30m telescopes - Zhao, G. Y.; Roy, A.; Wagner, Jan; Donoso, E.; Torne, Pablo; Ros, Eduardo; Lindqvist, Michael; Lobanov, A. P.; Ramakrishnan, Venkatessh; Krichbaum, T.P.; Rottmann, H.; Zensus, A.J.; et al. (RadioNet 4 Astronomy and Astrophysics, 2025)