 This choice of "q" implies that in the unique finite field F"q" of order "q", the element  −1 has a square root.Now let "V" = F"q" and let

If a pair {"a","b"} is included in "E", it is included under either ordering of its two elements.For, "a" − "b" = −("b" − "a"), and  −1 is a square, from which it follows that "a" − "b" is a square if and only if "b" − "a" is a square.