Renormalization of the three-boson system with short-range interactions   revisited
  We consider renormalization of the three-body scattering problem in low-energy effective field theory of self-interacting scalar particles by applying time-ordered perturbation theory to the manifestly Lorentz-invariant formulation. The obtained leading-order equation is perturbatively renormalizable and non-perturbatively finite and does not require a three-body counter term in contrast to its non-relativistic approximation. 
E. Epelbaum, J. Gegelia, Ulf-G. Mei{\ss}ner, De-Liang Yao
nucl-th