If you want to post an article in its completion, you must get permission from the copyright holder. It isn't enough to post a link and the author's name. You have to get permission. This is because the copyright holder (usually the author) has sole discretion over where his or her work is disseminated. This is why it's called "coyright"--the right to copy or produce).
You may, however, post an excerpt fro the article, as long as you credit your source. Usually the excerpt should not exceed 5% of the total length of the article. This is called fair use.
If you write a book and you want to quote someone, you don't need permission unless the size of your quote exceeds fair use. This is true of articles and prose, but NOT true of song lyrics and poems. If you want to quote even a single line of a song lyric or a poem, you have to get permission from the copyright holder. They don't fall under tha fair use policy.
HTH
