Fast Approximation of Support Vector Kernel Expansions, and an Interpretation of Clustering as Approximation in Feature Spaces. - Bernhard Schölkopf; Alexander J. Smola; Phil Knirsch; Chris Burges (DAGM-Symposium, 1998)

Input space versus feature space in kernel-based methods. - Bernhard Schölkopf; Sebastian Mika; Christopher J. C. Burges; Phil Knirsch; Klaus-Robert Müller; Gunnar Rätsch; Alexander J. Smola (IEEE Trans. Neural Networks, 1999)