de Carvalho, E. F., & Lopes, N. F. (1994). Growth, pigmentation and nitrogen fixation in <i>Azolla</i> spp. cultivated under four light flux denstms. Pesquisa Agropecuaria Brasileira, 29(2), 221–236. https://doi.org/10.1590/S1678-3921.pab1994.v29.4047