P. W.  Ball, ?Lunaria?, vol. 1, 1993.

P. W.  Ball, ?Ornithopus?, vol. 2, 1968.

P. W.  Ball, ?Bunias?, vol. 1, 1993.

P. W.  Ball and Reznicek, A. A., ?Carex?, in Flora of North America, vol. 23, Oxford University Press, 2002, pp. 254 - 572.