R.A. Brualdi, A.J. Hoffman
Linear Algebra and Its Applications
We show that the semilattice extension problem raised by Arbib and Manes in [2] is NP-hard, implying that no simple solution is likely to be forthcoming. © 1983 Birkhäuser Verlag.
R.A. Brualdi, A.J. Hoffman
Linear Algebra and Its Applications
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