Tier 1 - manual outrich links, high quality Tier 2 - cheap, but also not from gsa links Tier 3 - Articles (excluding GNU-board, as sites on this engine are low-quality), Wiki, Forum Tier 4 - Same like Tier 3 + Blog comment, Guestbook, Image comment, Social Bookmark
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Tier 2 - cheap, but also not from gsa links
Tier 3 - Articles (excluding GNU-board, as sites on this engine are low-quality), Wiki, Forum
Tier 4 - Same like Tier 3 + Blog comment, Guestbook, Image comment, Social Bookmark