DoFollow Links don't exist. They are just Follow Links
Somebody came up with "DoFollow", but the wrong wording even leads to broken HTML coding by non-experienced webmasters.
The correct term to use is "Follow Link".
You don't have to do anything to make a link "do follow". It is followed by robots, by default.
<a href="http://example.com">example link that is a FOLLOW link</a>
The coding above is the correct for a Follow link. No REL-attribute (as with NoFollow link) is required, and especially not the attributes "dofollow" as some may imply.
Refer to the link type specification in the HTML spec of the W3C here.
Please DO let us know if you find a "dofollow" HTML specification somewhere :)