From the dissertation:
“... some national news sources like The New York Times and The Washington Post are considered the “gatekeeper” or “elite” sources of news, in that they influence news coverage made in other national and regional newspapers.68 Analysis of these two newspapers gives an indication of reporting trends likely to be followed in other news reports.”
Actually....(speak of the devil) this is on topic...
http://www.freerepublic.com/focus/f-chat/3189668/posts