Hiroyuki Mitsuhara Hiroaki Ogata Kazuhide Kanenishi Yoneo Yano Do Children Understand Binary Numbers by Electric Card Game? 191-192 2007 conf/digitel/2007 DIGITEL http://doi.ieeecomputersociety.org/10.1109/DIGITEL.2007.22 db/conf/digitel/digitel2007.html#MitsuharaOKY07