Unique symmetric (66, 26, 10) design admitting an automorphism of order 55 (Q2746398)

This paper shows that the first known symmetric \((66, 26, 10)\) design, constructed by \textit{Tran Van Trung} [J. Comb. Theory, Ser. A 33, 201-204 (1982; Zbl 0519.05008)], is up to isomorphism the only symmetric \((66, 26, 10)\) design admitting an automorphism of order \(55\), and that a full automorphism group of the design is isomorphic to \(\text{Frob}_{55}\times{\mathcal D}_{10}\). This completes the classification of symmetric \((66, 26, 10)\) designs with an automorphism group of order \(55\).