@article{CTT100836956,
  author = {M. Umehara and K. Yamada},
  title = {Hypersurfaces with light-like points in a Lorentzian manifold},
  journal = {Journal of Geometric Analysis},
  year = 2019,
}

@article{CTT100836957,
  author = {S. Akamine and M. Umehara and K.Yamada},
  title = {Space-like maximal surfaces containing entire null lines in Lorentz-Minkowski 3-space},
  journal = {Proc. Japan Acad. Ser.A, Math. Sci.},
  year = 2019,
}

@article{CTT100836955,
  author = {Atsufumi Honda and Naokawa Kosuke and Masaaki Umehara and Kotaro Yamada},
  title = {Isometric realization of cross caps as formal power series and its applications},
  journal = {Hokkaido Mathematical Journal},
  year = 2019,
}

@article{CTT100836959,
  author = {Shoichi Fujimori and Yu Kawakami and Masatoshi Kokubu and Wayne Rossman and Masaaki Umehara and Kotaro Yamada},
  title = {Exceptional constant mean curvature one  catenoids in de Sitter 3-space},
  journal = {},
  year = 2019,
}