Universal effective action for O(n)-symmetric \lambda \phi^4 model from   renormalization group
  The RG expansions for renormalized coupling constants g_6 and g_8 of the 3D n-vector model are calculated in the 4-loop and 3-loop approximations respectively. Resummation of the RG series for g_6 by the Pade-Borel-Leroy technique results in the estimates for its universal critical values g_6^*(n) which are argued to deviate from the exact numbers by less than 0.3%. The RG expansion for g_8 demonstrates stronger divergence being much less suitable for getting reliable numerical estimates. 
A. I. Sokolov, E. V. Orlov, V. A. Ul'kov, and S. S. Kashtanov (Saint   Petersburg Electrotechnical University, St. Petersbur...