@conference {Via - QLMPIT - EUSIPCO2011, title = {Testing Quaternion Properness: Generalized Likelihood Ratios and Locally Most Powerful Invariants}, booktitle = {19th European Signal Processing Conference (EUSIPCO 2011)}, year = {2011}, month = {August}, address = {Barcelona, Spain}, author = {V{\'\i}a, Javier and Vielva, Luis} }