http://www.aish.com/jl/l/b/48964501.html
http://www.chabad.org/library/article_cdo/aid/710724/jewish/The-Basics-of-the-Upsherin.htm
http://www.thehalacha.com/attach/Volume3/Issue19.pdf
and of course the swcholars, pseudo-scholars of the CR
http://www.theyeshivaworld.com/coffeeroom/topic/the-upsherin-what-are-the-origins