RepeatsDB in 2021: improved data and extended classification for protein tandem repeat structures. - Lisanna Paladin; Martina Bevilacqua; Sara Errigo; Damiano Piovesan; Ivan Micetic; Marco Necci; Alexander Miguel Monzon; Maria Laura Fabre; José Luis López; Juliet F. Nilsson; Javier Ríos; Pablo Lorenzano Menna; et al. (Nucleic Acids Res., 2021)