@article{son2006ultrasonic,
  title = {An ultrasonic standing-wave-actuated nano-positioning walking robot: piezoelectric-metal composite beam modeling},
  journal = {Journal of vibration and control},
  volume = {12},
  number = {12},
  pages = {1293--1309},
  publisher = {Sage Publications},
  year = {2006},
  author = {Son, Kwon Joong and Kartik, Venkataraman and Wickert, Jonathan A and Sitti, Metin}
}