Characteristics of EAS and Primary Particle Mass Composition in the   Energy Region of $10^{17} - 3 \cdot 10^{19}$ eV by Yakutsk Data
  In the work the data of the Yakutsk complex EAS array and their comparison with calculation in the case of primary nuclei of different chemical elements are presented. The calculation by QGSJET model have been used interpreting experimental data. 
S.P. Knurenko, V.P. Egorova, A.A. Ivanov, V.A. Kolosov, I.T. Makarov,   Z.E. Petrov, I.Ye. Sleptsov, G.G. Struchkov