WCAG 2.0 Link Requirements

2.4.4 Link Purpose (In Context)
WCAG 2.0 Level A requirement
The purpose of each link can be determined from the link text alone or from the link text together with its programmatically determined link context, except where the purpose of the link would be ambiguous to users in general.
2.4.9 Link Purpose (Link Only)
WCAG 2.0 Level AAA requirement
A mechanism is available to allow the purpose of each link to be identified from link text alone, except where the purpose of the link would be ambiguous to users in general.