Barreto, F. C. P., M. A. P dos Santos, F. F. de Lima, and M. L. Oliveira. 2011. “Intercomparison Measurements of Activity of 99mTc and 131I in Nuclear Medicine Services in the City of Recife”. Scientia Plena 3 (7). https://www.scientiaplena.org.br/sp/article/view/656.