Original reference:
Shu, Y.; Parker, K. A.; Truhlar, D. G. “Dual-Functional Tamm-Dancoff Approximation: A Simple Linear Response Theory to Correctly Describe the Potential Energy Surfaces In the Vicinity of S1/S0 Conical Intersection” J. Phys. Chem. Lett. 2017, 8, 2107-2112. [link]
Related references:
Li, S. L.; Marenich, A. V.; Xu, X.; Truhlar, D. G. "Configuration Interaction-Corrected Tamm-Dancoff Approximation: A Time-Dependent Density Functional Method with the Correct Dimensionality of Conical Intersections" J. Phys. Chem. Lett. 2014, 5, 322-328. [link]
Shu, Y.; Parker, K. A.; Truhlar, D. G. “Dual-Functional Tamm-Dancoff Approximation: A Simple Linear Response Theory to Correctly Describe the Potential Energy Surfaces In the Vicinity of S1/S0 Conical Intersection” J. Phys. Chem. Lett. 2017, 8, 2107-2112. [link]
Related references:
Li, S. L.; Marenich, A. V.; Xu, X.; Truhlar, D. G. "Configuration Interaction-Corrected Tamm-Dancoff Approximation: A Time-Dependent Density Functional Method with the Correct Dimensionality of Conical Intersections" J. Phys. Chem. Lett. 2014, 5, 322-328. [link]