@article{article1b72790a,
title   = {Björling problem for spacelike, zero mean curvature surfaces in L-4},
author = {Asperti, Antonio Carlos and Vilhena, José Antonio Moraes},
year = {2006},
doi = {10.1016/j.geomphys.2005.01.006},
journal   = {Journal of Geometry and Physics}
}