de Carvalho, Edson Ferreira, and Nei Fernandes Lopes. 1994. “Growth, Pigmentation and Nitrogen Fixation in Azolla Spp. Cultivated under Four Light Flux Denstms”. Pesquisa Agropecuaria Brasileira 29 (2): 221-36. https://doi.org/10.1590/S1678-3921.pab1994.v29.4047.