I think beauty can be relative, but within an objective framework. The best example is perhaps the existance of the Golden Ratio in the human face. We can all recognise a beautiful person, yet we may have different preferences. I think there are a couple of variables here. One is the degree of flexibility of the ratio (due to its complexity, especially in a human face - a hansome man and a beautiful woman may both have well-proportioned faces, yet we can all tell a man from a woman). The second is phychological, and this is where the subjectivity comes in. For example, a woman may not be perceived to be particularly beautiful, yet a man may still find her attractive, due to personality, or some associative thinking (“this person reminds me of someone I liked”).
Of course, this is just a theory, and it’d be wrong to draw a conclusion, but the Golden Mean seems to me to be a good evidence for the existance of objective beauty.
As for links, I wouldn’t want to restrict you to the information that only I can give… try searching on google.com for “golden mean”, “golden ratio” or “golden section”. Happy hunting 