The best m-term approximation with respect to polynomials with constant   coefficients
  In this paper we show that that greedy bases can be defined as those where the error term using $m$-greedy approximant is uniformly bounded by the best $m$-term approximation with respect to polynomials with constant coefficients in the context of the weak greedy algorithm and weights. 
Pablo M. Bern\'a, \'Oscar Blasco
math.FA