Improvement of People Counting by Pairing Head and Face Detections from Still Images. - Thi-Oanh Ha 001; Hoang-Nhat Tran; Hong-Quan Nguyen; Thanh-Hai Tran 001; Phuong-Dung Nguyen; Huong-Giang Doan; Van-Toi Nguyen; Hai Vu; Thi-Lan Le (MAPR, 2021)