@articleHemsel_Priya_2006, title=Model based analysis of piezoelectric transformers, volume=44, Supplement, DOI=10.1016/j.ultras.2006.05.086, number=0, journal=Ultrasonics, author=Hemsel, Tobias and Priya, S, year=2006, pages=e741–e745 

@inproceedingsHemsel_Littmann_Wallaschek_2002, title=Piezoelectric transformers - state of the art and development trends, volume=1, DOI=10.1109/ULTSYM.2002.1193485, number=vol.1, booktitle=Ultrasonics Symposium, 2002. Proceedings. 2002 IEEE, author=Hemsel, Tobias and Littmann, Walter and Wallaschek, Jörg, year=2002, pages=645–648