1. Yu. V. Pokornyi, Zh. I. Bakhtina, M. B. Zvereva, and S. A. Shabrov, Sturm Oscillation Method in Spectral Problems (Fizmatlit, Moscow, 2009) [in Russian].
2. Yu. V. Pokornyi, O. M. Penkin, V. L. Pryadiev, A. V. Borovskikh, K. P. Lazarev, and S. A. Shabrov, Differential Equations on Geometric Graphs (Fizmatlit, Moscow, 2004) [in Russian].
3. B. Dekoninck and S. Nicase, “The Eigenvalue Problem for Network of Beams,” in Generalized Functions, Oper. Theory and Dynamical Systems (Chapman and Hall Research in Math., 1999), pp. 335–344.
4. B. Dekoninck and S. Nicase, “Control of Network of Euler-Bernoulli Beams,” ESAIM: Control Optim. and Calculus of Variations 4, 57–82 (1999).
5. J. E. Lagnese, G. Leugering, and E. J. P. G. Schmidt, “Control of Planar Networks of Timoshenko Beams,” SIAM J. Control Optim. 31, 780–811 (1993).