How many years did it take the modern engineers to figure out how the roman concrete was made out of?

Why was the emancipation proclamation widely attacked when it was written?

Who founded the social contract theory of the government

Historians have recently discovered a historical journal published in the early twentieth century. the journal contains facts based on original sources about the downfall of the early byzantium empire. historians consider this long-lost journal to be a breakthrough in their understanding of the byzantium empire. based on this information, the journal is a source.