By the time Martin Luther King Jr. was assassinated, he had been a civil rights leader for more than ten years.
decided to run in the next presidential election.
led the Democratic Party for more than ten years.
decided to lead a demonstration supporting the war.

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.