@INPROCEEDINGS{ist:michalowsky16a, author = {Michalowsky, S. and Ebenbauer, C.}, title = {Gradient approximation and extremum seeking via needle variations}, booktitle = {Proc.\ American Control Conf.\ (ACC)}, year = {2016}, pages = {6091-6096}, address = {Boston, MA, USA}, pubtype = {proceeding} }