1. J. Dimitrov, Reliability of Railway Vehicles (VMEI “V. I. Lenin”, Sofia, 1989), p. 349 (in Bulgarian).
2. A. D. Puzankov, Determination of Reliability Parameters of Locomotive Parts and Units: Methodological Instructions for Practical Classes (MIIT, Moscow, 1990), (in Russian).
3. R. Fr. Stapelberg, Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design (Springer-Verlag, London, 2009), p. 826.
4. Numerical study of the hydraulic excavator overturning stability during performing lifting operations
5. National Company of Railway Infrastructure, “Instruction for Repair of Wagons, Rail Self-Propelled Specialized Machines and Equipment with Increased Danger” (NRIC, Sofia, 2013), available at https://www.rail-infra.bg/, (in Bulgarian).