returns the values from bidimensional cumulative for (s,t) sample using (theta,delta) parameters.
References
Veronica A. Gonzalez-Lopez and Nelson I. Tanaka. Bi-variate Data Modeling Through Generalized Archimedean Copula RT-MAE 2003-03. Harry Joe. Multivariate Models and Dependence Concepts Monogra. Stat. & Appl. Probab. 73. Chapman and Hall (1997)