Gramacy, R. B. (2007). tgp: An R Package for Bayesian Nonstationary, Semiparametric Nonlinear Regression and Design by Treed Gaussian Process Models.
Journal of Statistical Software, 19(9).
http://www.jstatsoft.org/v19/i09
Robert B. Gramacy, Matthew Taddy (2010). Categorical Inputs,
Sensitivity Analysis, Optimization and Importance Tempering with tgp
Version 2, an R Package for Treed Gaussian Process Models.
Journal of Statistical Software, 33(6), 1--48.
http://www.jstatsoft.org/v33/i06/.
Gramacy, R. B., Lee, H. K. H. (2007).
Bayesian treed Gaussian process models with an application to computer modeling
Journal of the American Statistical Association, to appear.
Also available as ArXiv article 0710.4536
http://arxiv.org/abs/0710.4536
http://bobby.gramacy.com/r_packages/tgp