1. Mechanics;Landau,1976
2. Mathematical Methods of Classical Mechanics;Arnold,1989
3. Oscillation Matrices and Kernels and Small Vibrations of Mechanical Systems;Gantmacher,1961
4. J. Feinberg, Density of Eigenvalues in a Quasi-Hermitian Random Matrix Model - the Case of Indefinite Metric, talk at the conferences: *Non-Hermitian Physics - PHHQP XVIII, ICTS, Bengaluru, India, 2018, https://www.icts.res.in/program/nhp2018/talks *The ISF Research Workshop: Random Matrices, Integrability and Complex Systems. Yad Hashmona, October (2018) 3-8, http://eugenekanzieper.faculty.hit.ac.il/yad8/2018/pages/schedule.html.