On weight graphs for nilpotent Lie algebras I
  We introduce the concept of weight graph for the weight system $P\frak{g}(T)$ of a finite dimensional nilpotent Lie algebra $\frak{g}$ and analyze the necessary conditions for a $(p,q)$-graph to be a weight graph for some $\frak{g}$. 
Otto Rutwig Campoamor, Jose Maria Ancochea