1K. Nakagawa, K. Andoh and S. J. Duan. A design method of structure to minimize the square sum of natural periods of vibration[J].Computers & Structures, 1992,45 (3) : 587-591.
2H. J. Zhu, K. Nakagawa, and S. J. Duan. A study on optimization of power transmission pylons by minimization of the square of the natural periods[J] .Computers & Structures,1996,59(3):805-812.