Project 3742: R. M. Saunders, K. Fowler. 1993. The supraspecific taxonomy and evolution of the fern genusAzolla (Azollaceae). Plant Systematics and Evolution. 184 (3-4):175-193.
Saunders, R. M. and Fowler, K. 1993. The supraspecific taxonomy and evolution of the fern genusAzolla (Azollaceae). Plant Systematics and Evolution. Vol. 184(3-4), pp. 175-193.