Sienz, J., Ollar, J., Mortished, C., Jones, R., & Toropov, V. (2017). Gradient based hyper-parameter optimisation for well conditioned kriging metamodels. Structural and Multidisciplinary Optimization, 55(6), pp. 2029-2044. doi:10.1007/s00158-016-1626-8

Sienz, Johann, Jonathan Ollar, Charles Mortished, Royston Jones, and Vassili Toropov. "Gradient Based Hyper-parameter Optimisation for Well Conditioned Kriging Metamodels." Structural and Multidisciplinary Optimization 55, no. 6 (2017): 2029-2044.

Sienz, Johann, et al. "Gradient Based Hyper-parameter Optimisation for Well Conditioned Kriging Metamodels." Structural and Multidisciplinary Optimization 55.6 (2017): 2029-2044.