Nonredundant 1's in Gamma-Free Matrices

@article{Spinrad1995Nonredundant1I,
  title={Nonredundant 1's in Gamma-Free Matrices},
  author={Jeremy P. Spinrad},
  journal={SIAM J. Discrete Math.},
  year={1995},
  volume={8},
  pages={251-257}
}