Structural, syntactic, and statistical pattern recognition joint IAPR International Workshops, S+SSPR 2020, Padua, Italy, January 21-22, 2021 : proceedings - Torsello, Andrea; Rossi, Luca 1980-; Pelillo, Marcello 1966-; Biggio, Battista; Robles-Kelly, Antonio (Image processing, computer vision, pattern recognition, and graphics, 2021)