Feifei Gao Arumugam Nallanathan Yide Wang Improved MUSIC Under the Coexistence of Both Circular and Noncircular Sources. 3033-3038 2008 56 IEEE Transactions on Signal Processing 7-1 http://dx.doi.org/10.1109/TSP.2007.916123 db/journals/tsp/tsp56.html#GaoNW08