R. Development and C. Team, R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, 2007.

D. A. Girard, Asymptotic near-efficiency of a "Gibbs-energy" estimating-function approach for fitting Matern covariance models to a dense (noisy) series, 2009.

D. A. Girard, A fast, near efficient, randomized-trace based method for fitting continuous stationary correlation models to large noisy data sets in the case of a single range-parameter, p.2010

R. Furrer, D. Nychka, and S. Sain, fields: Tools for spatial data, 2011.