http://www.sciencedirect.com/science/article/pii/S1090780707000444 (Publisher version)
Schulte, R., Henning, A., Tsao, J., Boesiger, P., & Pruessmann, K. (2007). Design of broadband RF pulses with polynomial-phase response. Journal of Magnetic Resonance, 186(2), 167-175. doi:10.1016/j.jmr.2007.02.004.