@article {852, title = {Properties of real and complex ETFs and their application to the design of low coherence frames}, journal = {Linear Algebra and its Applications}, volume = {508}, year = {2016}, month = {November, 2016}, pages = {81-90}, url = {http://www.sciencedirect.com/science/article/pii/S0024379516302555}, author = {Cristian Rusu and Nuria Gonz{\'a}lez-Prelcic and Robert W. Heath Jr.} }