The Atacama Cosmology Telescope: arcminute-resolution maps of 18 000 square degrees of the microwave sky from ACT 2008–2018 data combined with Planck. Issue 12 (1st December 2020) - Naess, Sigurd; Aiola, Simone; Austermann, Jason E.; Battaglia, Nick; Beall, James A.; Becker, Daniel T.; Bond, Richard J.; Calabrese, Erminia; Choi, Steve K.; Cothard, Nicholas F.; Crowley, Kevin T.; Darwish, Omar; et al.