@article{CTT100836989,
  author = {S. Akamine and A. Honda and M. Umehara and K.Yamada},
  title = {Bernstein-type theorem for zero mean curvature hypersurfaces without time-like points in Lorentz-Minkowski space},
  journal = {Bulletin of the Brazilian Mathematical Society, New Series},
  year = 2020,
}

@article{CTT100684951,
  author = {Hasegawa Masaru and Honda Atsufumi and Kosuke Naokawa and Masaaki Umehara and Kotaro Yamada},
  title = {Intrinsic invariants of Cross Caps},
  journal = {Selecta Math. New Ser.},
  year = 2014,
}