Petre Stoica Niclas Sandgren Total-Variance Reduction Via Thresholding: Application to Cepstral Analysis. 66-72 2007 55 IEEE Transactions on Signal Processing 1 http://doi.ieeecomputersociety.org/10.1109/TSP.2006.882073 db/journals/tsp/tsp55.html#StoicaS07