@article{CTT100875616,
  author = {Atsufumi Honda and Kosuke Naokawa and Kentaro Saji and Masaaki Umehara and Kotaro Yamada},
  title = {On the existence of four or more curved foldings with common creases and crease patterns},
  journal = {Beiträge zur Algebra und Geometrie / Contributions to Algebra and Geometry},
  year = 2021,
}

@article{CTT100849149,
  author = {Masaaki Umehara and Kotaro Yamada},
  title = {Hypersurfaces with light-like points in a Lorentzian manifold II},
  journal = {Kodai Math. J.},
  year = 2021,
}