  Using non-relativistic effective Lagrangians in the particle-dimer picture,
we rederive the expression for the energy shift of a loosely bound
three-particle bound state of identical bosons in the unitary limit. The
effective field theory formalism allows us to investigate the role of the
three-particle force, which has not been taken into account in the earlier
treatment of the problem. Moreover, we are able to relax the requirement of the
unitary limit of infinite scattering length and demonstrate a smooth transition
from the weakly bound three-particle state to a two-particle bound state of a
particle and a deeply bound dimer.
