Ricci, Marta dos Santos Freire, et al. “Nutrient Contents of Two Lettuce Cultivars Fertilized With Organic Compost”. Pesquisa Agropecuaria Brasileira, vol. 30, no. 8, Aug. 1995, pp. 1035-9, doi:10.1590/S1678-3921.pab1995.v30.4394.