?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.au=Nguyen%2C+Dong+Anh&rft.aulast=Nguyen&rft.aufirst=Dong+Anh&rft.date=2015&rft.atitle=1%2F3+SUBHARMONIC+RESPONSE+OF+DUFFING+OSCILLATOR+UNDER+PERIODIC+AND+RANDOM+EXCITATIONS&rft.title=Journal+Bulletin+DGTU&rft.genre=article