Question : A user named P3sn from Netherlands asks Matt cutts ”What are Correct quotations in Google. How can you quote correctly from different sources without getting penalized for duplicated content? Is it possible to quote and refer to the source? ”
Answer By Matt cutts : He clearly states that if you are writing a post and you find something valuable related to that post on another site then you can quote that information in a block with a link pointing to that article because google have some very good techniques or methods which can clearly find out that you have copied some piece of content to make your post more valuable and in view of google, it is completely legitimate.
But you can not copy a entire article with a link pointing to that site. If you do that sort of thing than you can hurt your site in “Google SERP”
This is what matt cutts states in a video at Youtube