  One of the very first results about designs over finite fields, by S. Thomas,
is the existence of a cyclic 2-$(n,3,7)$ design over $\mathbb{F}_{2}$ for every
integer $n$ coprime with 6. Here, by means of difference methods, we reprove
and improve a little bit this result showing that it is true, more generally,
for every odd $n$. In this way, we also find the first infinite family of
non-trivial cyclic group divisible designs over $\mathbb{F}_{2}$.
