Cho, Jung Jin; Chen, Yong; Ding, Yu (2007), "On the (co)girth of a connected matroid", Discrete Applied Mathematics, 155 (18): 2456–2470, doi:10.1016/j.dam.2007.06.015, MR2365057.
Cho, Chen & Ding (2007) observe that this is a corollary of a result of Alexander Vardy in coding theory: Vardy, Alexander (1997), "The intractability of computing the minimum distance of a code", IEEE Transactions on Information Theory, 43 (6): 1757–1766, doi:10.1109/18.641542, MR1481035.
Cho, Chen & Ding (2007) observe that this is a corollary of a result of Alexander Vardy in coding theory: Vardy, Alexander (1997), "The intractability of computing the minimum distance of a code", IEEE Transactions on Information Theory, 43 (6): 1757–1766, doi:10.1109/18.641542, MR1481035.