Littelmann's path crystal and combinatorics of certain sl_{l+1}^ modules   of level zero
  We construct a subcrystal of the Littelmann's path crystal whose formal character coincides with that of a certain simple integrable module of level zero over the untwisted affine Lie algebra associated to sl_n. We also establish an analogue of the Littlewood-Richardson rule for the tensor product of that crystal with a highest weight crystal. 
Jacob Greenstein