Vieira, R.M.L. 1992. Some general principles of coin conservation and the mechanical cleaning process adopted by the Museu Histórico Nacional. Revista do Museu de Arqueologia e Etnologia. 2 (Dec. 1992), 133–136. DOI:https://doi.org/10.11606/issn.2448-1750.revmae.1992.108999.