http://www.copyright.gov/title17/92chap1.html#107
§ 107. Limitations on exclusive rights: Fair use
Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include —
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
This is an interpretable law but in general it allows you to use small portions of text from copyrighted material if for example you wanted to post it here. If you're going to do this only use a few sentences, quote the text and provide a link to the whole article.
In this example I'll be using a page from my own site but lets pretend its from somewhere else. If for example our discussion was regarding capturing VHS video and the effects of false macrovision protection we may want to quote this:
This would be acceptable:
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http://www.nepadigital.com/mv/
What is Macrovision Protection
Macrovision was first used on VHS tapes in 1984 to copy protect video on VHS tapes, it is simply a video error inserted into the video stream of most commercial VHS tapes. This does not affect how it looks when viewing it on a TV, TV's are very forgiving of this error. Note that there are some exceptions, this did affect some older TV's when first introduced. What it will affect is attempts to copy a commercial VHS tape from one VCR to another. This manifests as video that jumps frames, video flashing from bright to dark such as the strobing affect I described above. Some of these symptoms very closely resemble a tracking problem. They can however vary widely especially with capture devices, some may simply put up screen stating the video is copyright protected.
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My choice of article is ironic isn't it?
I've only quoted a relatively small part of the entire article. If for example you were quoting a news article you'd want to follow the same format. Quote the first paragraph or relevant text elsewhere in the article and provide a link to full article.
