“…We also refer to Bradley et al (2016), Chilès and Desassis (2018), Damianou (2015), Guinness (2018), Meng and Ng (2016), Nickson et al (2015), Sung et al (2016), Tzeng and Huang (2018), and Van Stein et al (2017). We, however, focus on the method that is detailed in Gramacy (2016) and Gramacy and Apley (2015), and compare our methods with Gramacy's method (Gramacy's method is also compared with a new method in Guhaniyogi and Banerjee (2018)). We observe that two NN variations are used in Gramacy (2016, Section 3.1) and Gramacy and Apley (2015, Fig.…”