  The purpose of this paper is to extend a result by Donoho and Huo, Elad and
Bruckstein, Gribnoval and Nielsen on sparse representations of signals in
dictionaries to general matrices. We consider a general fixed measurement
matrix, not necessarily a dictionary, and derive sufficient condition for
having unique sparse representation of signals in this matrix. Currently, to
the best of our knowledge, no such method exists. In particular, if matrix is a
dictionary, our method is at least as good as the method proposed by Gribnoval
and Nielsen.
