@article{Nanda2017, author = "Kaushik D. Nanda and Anna I. Krylov", title = "{Visualizing the Contributions of Virtual States to Two-Photon Absorption Cross Sections by Natural Transition Orbitals of Response Transition Density Matrices}", year = "2017", month = "7", url = "https://acs.figshare.com/articles/journal_contribution/Visualizing_the_Contributions_of_Virtual_States_to_Two-Photon_Absorption_Cross_Sections_by_Natural_Transition_Orbitals_of_Response_Transition_Density_Matrices/5173687", doi = "10.1021/acs.jpclett.7b01422.s001" }