@article{HofukuChoNishidaetal.2013,
  author    = {Yoyoi Hofuku and Shinya Cho and Tomohiro Nishida and Susumu Kanemune},
  title     = {Why is programming difficult?},
  journal   = {Commentarii informaticae didacticae : (CID)},
  series    = {proposal for learning programming in "small steps" and a prototype tool for detecting "gaps"},
  number    = {6},
  pages     = {13 -- 24},
  year      = {2013},
}