To determine if an online source is credible, the most effective approach from the options provided would be to check the links listed as sources to see if they are trustworthy. This involves evaluating the references the author uses to support their claims, ensuring those references come from reputable, reliable, and trustworthy sources.
While all the other options may contribute to assessing credibility, verifying the quality of the sources cited is a direct method to gauge the overall reliability of the information presented.