Bifurcation of 3-Torus Attractor in Certain Continuous-Time Dynamical Systems**The work of the third author (T.E.) is partially supported by Grant-in-Aid of Scienti_c Research (KAKENHI) (C) No. 24560556 and by Grant-in-Aid of Special Research Project by Institute of Science and Technology, Meiji University. The authors would like to thank these grants.