http://papers.nips.cc/paper/2193-hyperkernels.pdf (Publisher version)
Ong, C., Smola, A., & Williamson, R. (2003). Hyperkernels. In S. Becker, S. Thrun, & K. Obermayer (Eds.), Advances in Neural Information Processing Systems 15 (pp. 495-502). Cambridge, MA, USA: MIT Press.