  A tournament is an oriented complete graph. The problem of ranking
tournaments was firstly investigated by P. Erd\H{o}s and J. W. Moon. By
probabilistic methods, the existence of "unrankable" tournaments was proved. On
the other hand, they also mentioned the problem of explicit constructions.
However, there seems to be only a few of explicit constructions of such
tournaments. In this note, we give a construction of many such tournaments by
using skew Hadamard difference sets which have been investigated in
combinatorial design theory.
