Deep Underground Neutrino Experiment (DUNE) Near Detector Conceptual Design Report. - Abud, A. Abed; Abi, B.; Acciarri, R.; Acero, M. A.; Adamov, G.; Adams, D.; Adinolfi, M.; Aduszkiewicz, A.; Ahmad, Z.; Ahmed, J.; Alion, T.; Monsalve, S. Alonso; et al. (Instruments (2410-390X), 2021)