@Article PGS06,
author = "Pigache, Fran\c{c}ois and Giraud, Fr\'ed\'eric and Semail, Betty",
title = "Modelling and identification of a planar standing wave ultrasonic motor ",
journal = "European Journal of Applied Physics",
number = "1",
volume = "34",
pages = "55--65",
year = "2006",
}