The hit problem for the polynomial algebra of four variables
  We study the problem of determining a minimal set of generators for the polynomial algebra $\mathbb F_2[x_1,x_2,...,x_k]$ as a module over the mod-2 Steenrod algebra $\mathcal{A}$. In this paper, we give an explicit answer in terms of the monomials for $k=4$. 
Nguyen Sum
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