Driving concepts for bundled ultrasonic linear motors
M. Mracek, T. Hemsel, T. Sattel, P. Vasiljev, J. Wallaschek, Journal of Electroceramics 20 (2008) 153–158.

Piezoelectric linear motor concepts based on coupling of longitudinal vibrations
T. Hemsel, M. Mracek, J. Twiefel, P. Vasiljev, Ultrasonics 44, Supplement (2006) e591–e596.

Synergetic driving concepts for bundled miniature ultrasonic linear motors
M. Mracek, T. Hemsel, Ultrasonics 44, Supplement (2006) e597–e602.

Survey of the present state of the art of piezoelectric linear motors
T. Hemsel, J. Wallaschek, Ultrasonics 38 (2000) 37–40.

State of the art and development trends of ultrasonic linear motors
T. Hemsel, J. Wallaschek, in: Ultrasonics Symposium, 2000 IEEE, 2000, pp. 663–666 vol.1.