Schumm, B. A., Dokshitzer, Y. L., Khoze, V. A., Koetke, ,., & Dale, S. (1992). Average charged multiplicity of events containing heavy quarks in e⁺e⁻ annihilation. Physical Review Letters, 69, 3025-3028. https://doi.org/10.1103/physrevlett.69.3025