  We discuss the interchangeability of the thermodynamic limit \beta \to \infty
and the infinite limit of the Trotter number n \to \infty when Trotter formula
e^{H_{0}+V} =\lim_{n \to \infty} (e^{H_{0}/n} e^{V/n}) is used to calculate
partition functions with Hamiltonians of the form H=H_{0}+V.
