DDOTI observations of gravitational-wave sources discovered in O3. - Becerra, R L; Dichiara, S; Watson, A M; Troja, E; Butler, N R; Pereyra, M; Moreno Méndez, E; De Colle, F; Lee, W H; Kutyrev, A S; López, K O C (Monthly Notices of the Royal Astronomical Society, 2021)