An isoperimetric function for Stallings' group
  We prove that $n^{7/3}$ is an isoperimetric function for a group of Stallings that is finitely presented but not of type $\mathcal{F}_3$. Note: The authors with Robert Young have now proved a quadratic Dehn function for this group. See arXiv:0712.3877 
Will Dison, Murray Elder and Timothy R Riley