“…Note that preservation of the second-order structure in the ROM allows a meaningful physical interpretation and usually provides more accurate approximations, and an ROM which preserves the structural properties such as stability and passivity is highly desirable. Therefore, on the contrary, structure-preserving MOR techniques for second-order form systems are proposed, which have received a lot of attention during the last few years, including moment matching methods based on Krylov subspaces (Bai and Su, 2005;Jbilou and Kaouane, 2019;Xu et al, 2018), families of BT methods (Chahlaoui et al, 2006;Haider et al, 2019;Reis and Stykel, 2008;Uddin, 2020) and orthogonal polynomial methods (Qiu et al, 2018;Xiao et al, 2019b;Xiao and Jiang, 2014). Overview articles of different reduction methods are given in Antoulas (2005), Benner et al (2017), Jiang (2010) and the references therein.…”