What is a document that was produced during the same time period as the historical event?

That would be a primary source, It's a document that was was made during the time being studied. Meaning it was written during the time period it talks about

although the legal justifications for the trials and their procedural innovations were controversial at the time, the nuremberg trials are now regarded as a milestone toward the establishment of a permanent international court, and an important precedent for dealing with later instances of genocide and other crimes

this isn't a question and if you're going to list things be kind and use commas.