  By using the Wang-Landau flat-histogram Monte Carlo (MC) method for very
large lattice sizes never simulated before, we show that the phase transition
in the frustrated Heisenberg stacked triangular antiferromagnet is of
first-order, contrary to results of earlier MC simulations using old-fashioned
methods. Our result lends support to the conclusion of a nonperturbative
renormalization group performed on an effective Hamiltonian. It puts an end to
a 20-year long controversial issue.
