“Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields”, P.R. Zangara, S. Dhomkar, A. Ajoy, K. Liu, R. Nazarian, D. Pagliero, D. Suter, J.A. Reimer, A. Pines, C.A. Meriles, Proc. Natl. Acad. Sci. USA 116, 2512 (2019). Available as arXiv:1902.06805.