Analysis of information sources in references of the Wikipedia article "Empire of Brazil" in English language version.
A primeira estimativa oficial para a extensão superficial do território brasileiro data de 1889. O valor de 8,337,218 km2 (3,219,018 sq mi) foi obtido a partir de medições e cálculos efetuados sobre as folhas básicas da Carta do Império do Brasil, publicada em 1883. [The first official estimate of the surface area of the Brazilian territory dates from 1889. A value of 8,337,218 km2 (3,219,018 sq mi) was obtained from measurements and calculations made on drafts of the Map of the Empire of Brazil, published in 1883.]