Kozhevnikova, Marina E., et al. “Non-Perturbative Quantum Chromodynamics and Short Strings in Electron-Positron Pair Annihilation to Hadrons”. Journal of the Belarusian State University. Physics, no. 2, May 2019, pp. 4-15, https://doi.org/10.33581/2520-2243-2019-2-4-15.