Estimation of Difficulty When Reading VR-based Educational Comics Using Gaze, Facial Movement, Heart Rate, and Electroencephalography. - Hiroyuki Ishizuka; Kenya Sakamoto; Shizuka Shirai; Yutaro Hirao; Monica Perusquía-Hernández; Hideaki Uchiyama; Kiyoshi Kiyokawa (APMAR, 2024)