The all-pass filtered-x algorithm. - John Garas; Piet C. W. Sommen (EUSIPCO, 1998)

Using phase information to decorrelate the filtered-x algorithm. - Piet C. W. Sommen; John Garas (ICASSP, 1998)

Warped linear time invariant systems and their application in audio signal processing. - John Garas; Piet C. W. Sommen (ICASSP, 1999)