In which type of historical reading material would you be most likely to find a newspaper editorial from a particular time period?

If you were to find a newspaper editorial from a particular time period and you wanted to use it as historical evidence then it would be a "primary source", since it offers an "unaltered" view into the past. 

Upon the fall of rome, europe ceased being influenced by the cultures of the mediterranean coast and was more influenced by germanic tribal confederations that had already taken over vast swathes of roman territory, although the influence of rome on the former empire was very strong in legal