Ryo Ishizuka, Hironori Washizaki, Yoshiaki Fukazawa, Shinobu Saito and Saori Ouji, “Categorizing and visualizing issue tickets to better understand the features implemented in existing software systems,” The 10th International Workshop on Empirical Software Engineering in Practice (IWESEP 2019), Tokyo, Japan, on December 13-14, 2019.