On continuity of Guo Wuwen function
  We show that the functions g and gs introduced by Guo Wuwen in [4] are continuous and semialgebraic. We use this fact to prove that the set Nn of ordered n-tuples of real numbers, realizable by nonnegative matrices, is a closed set. 
Z. Ambro\.zy, I. Biborski
math.AG