How impactful were the political, economic & technological changes during the presidencies of Reagan, George H. W Bush, Clinton,George w. Bush, & Obama

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.