The Head of the Geotechnical Engineering Office, Mr Wong Hok-ning (centre), Mr Wai Kee-shun (right) and Mrs Helen Yu Lai Ching-ping, attended the "HK Landslides" e-book launch briefing today (February 20). Mr Wai and Mrs Yu, who witnessed the landslides at Po Shan Road and Sau Mau Ping in 1972 respectively, shared their stories at the briefing.