"Hmm, Did You Hear What I Just Said?": Development of a Re-Engagement System for Socially Interactive Robots. - Hoang-Long Cao; Paola Cecilia Torrico Moron; Pablo Gómez Esteban; Albert De Beir; Elahe Bagheri; Dirk Lefeber; Bram Vanderborght (Robotics, 2019)