@article{CTT100916180,
  author = {Masaaki Umehara and Naoya Ando},
  title = {Umbilics of surfaces in the Lorentz-Minkowski 3-space},
  journal = {Results Math.},
  year = 2023,
}

@article{CTT100916175,
  author = {Atsufumi Honda and Naokawa Kosuke and Kentaro Saji and Masaaki Umehara and Kotaro Yamada},
  title = {Symmetries of cross caps},
  journal = {TOHOKU MATH. J.},
  year = 2023,
}