They are listed as “partly-secret” or “quasi-secret” because technically they are in the public domain. You are just not allowed to read them 
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These are reports by the Congressional Research Service. Some consider them to be largely fair and balanced, which is why they are not wanted to be seen. (This is not a left vs. right thing. If a politician is pushing for legislation, they cheerleader in just one direction. They tend to say “X is 100% bad” not “X is 80% bad but has some positives under certain circumstances.” Their opponents say “X is 100% good”, not “X is 80% good, but it causes harm under certain circumstances.” Mixed messages don’t sell well. (This is not a political show, so I hope I’m not going to far by saying this.)
How did they get the reports? They don’ t seem to say. Technically, they have broken the law without breaking any actual laws.
Interested in reading some of it?:
http://wikileaks.org/wiki/Change_you_can_download:_a_billion_in_secret_Congressional_reports