How many materials needed to facilitate the middle age and elderly to learn using smartphones? - Ying-Li Lee; Tzuning Wen; Sheng Chieh Lu; Chia Wei Lin; Ching-lin Lai; Meng-Ping Wu; Shuo-Ju Chiang; Mei-Ju Chen; Chien-Hsien Lee; Polun Chang (AMIA, 2013)