Leaving and Cleaving - A study of the two daughters-in-law of Naomi from a Christian perspective. - http://www.bayou.com/~lou2247/ruth02.html
Jewish Encyclopedia: Orpah - Overview of Naomi's other daughter-in-law from the traditional Jewish perspective, including rabbinic commentary. - http://www.jewishencyclopedia.com/view.jsp?artid=141&letter=O