BibTex format
@book{Krener:2005,
author = {Krener, AJ and Kang, W and Hamzi, B and Tall, IA},
publisher = {Springer Verlag},
title = {Low codimension control singularities for single input nonlinear systems},
url = {http://www.math.duke.edu/~hamzi/low_codim.pdf},
year = {2005}
}