De Carvalho EA, Andrade PP, Silva NH, Pereira EC, Figueiredo RC. Effect of usnic acid from the lichen Cladonia substellata on Trypanosoma cruzi in vitro: an ultrastructural study. Micron. 2005;36(2):155–61. doi: 10.1016/j.micron.2004.09.003. PMID: 15629646.