@article{article0b5d2159,
title   = {On the singularities of families of curve congruences on Lorentzian surfaces},
author = {Nabarro, Ana Claudia and Saloom, Amani},
year = {2016},
doi = {10.1007/s10883-015-9300-9},
journal   = {Journal of Dynamical and Control Systems}
}