D. W.  Bierhorst, ?Observations  on Schizaea and Actinostachys spp., including A. oligostachys sp. nov.?, Amer. J. Bot., vol. 55, pp. 87 - 108, 1968.

D. W.  Bierhorst, ?Structure and development of the gametophyte of Psilotum nudum?, Amer. J. Bot., vol. 40, pp. 649 - 658, 1953.