@article{Okada19,
  title = {Foreword},
  author = {Hiraku Okada},
  year = {2019},
  url = {http://search.ieice.org/bin/summary.php?id=e102-b_4_659},
  researchr = {https://researchr.org/publication/Okada19},
  cites = {0},
  citedby = {0},
  journal = {IEICE Transactions},
  volume = {102-B},
  number = {4},
  pages = {659},
}