1. F. Brackx, R. Delanghe, and F. Sommen, Clifford Analysis, Pitman Publishers: Boston-London-Melbourne, 1982.
2. F. Brackx, N. De Schepper, and F. Sommen, “The Clifford-Fourier Transform,” Journal of Fourier Analysis and Applications, Vol. 11, No. 6, pp. 669–681, December 2005.
3. F. Brackx, N.De Schepper, and F. Sommen, “The co-axial Fourier transform in Clifford analysis,” Journal of Mathmatical Imaging and Vision.
4. T. Bülow, “Hypercomplex spectral signal representations for the processing and analysis of images,” PhD Thesis, Christian-Albrechts-Universität, Institut für Informatik und Praktische Mathematik, Kiel, 1999.
5. T. Bülow and G. Sommer, “Quaternionic Gabor filters for local structure classification,” in 14th International Conference on Pattern Recognition, Brisbane, Australia, pp. 808–810, 1998.