О сильно регулярных расширениях обобщенных четырехугольников с короткими прямыми

We prove that a strongly regular graph such that the neighbourhoods of its vertices are point graphs of generalized quadrangles with 4-point lines coincides with the quotient of the Johnson graph on 4-element subsets of an 8-element set, or with the graph of rank 3 for the unitary group $U_5(2)$, or with the McLaughlin graph.
This work was supported by the Russian Foundation for Basic Research, Grant 93–011–1529.