aside from nofollow, that someone mentioned, you might want to implement http://en.wikipedia.org/wiki/Canonical_link_element http://en.wikipedia.org/wiki/Canoni

aside from nofollow, that someone mentioned, you might want to implement http://en.wikipedia.org/wiki/Canonical_link_element http://en.wikipedia.org/wiki/Canonical_link_element or put a block on year= into the robots.txt file