The Online Protein Processing Resource (TOPPR): a database and analysis platform for protein processing events. - Niklaas Colaert; Davy Maddelein; Francis Impens; Petra Van Damme; Kim Plasman; Kenny Helsens; Niels Hulstaert; Joël Vandekerckhove; Kris Gevaert; Lennart Martens (Nucleic Acids Res., 2013)