'Nonlinear adjoint sensitivity analysis' (Electromagnetic Waves, 2017), 'Adjoint Sensitivity Analysis of High Frequency Structures with MATLAB®', Chap. 8, pp. 193-219, DOI: 10.1049/SBEW525E_ch8
IET Digital Library, https://digital-library.theiet.org/;jsessionid=9v4shmpp4vko.x-iet-live-01content/books/10.1049/sbew525e_ch8