http://webschool.wash.k12.ut.us/language/lessons/possessivenouns.html
http://www.wisc-online.com/Objects/ViewObject.aspx?ID=wcn1601
http://www.rhlschool.com/eng3n9.htm
http://www.yourdictionary.com/grammar-rules/Possessive-Nouns.html
http://ethemes.missouri.edu/themes/1492
http://www.lexington1.net/technology/instruct/ppts/LAppts/35/possessivenouns.ppt.
http://www.harcourtschool.com/activity/possessive_noun/index.html
http://www.softschools.com/quizzes/grammar/possessive_nouns/quiz327.html
http://www.english-zone.com/spelling/possessives.html
http://www.grammar-quizzes.com/agr_possessives.html
http://www.mcwdn.org/grammar/nounpossess.html
http://www.ccc.commnet.edu/sensen/part2/fourteen/spelling_possessive.html
http://www.edufind.com/english/grammar/possesive1.cfm
http://www.meredith.edu/grammar/plural.htm
http://www.grammarmudge.cityslide.com/articles/article/426348/4944.htm
http://www.quia.com/jg/67716list.html
http://www.lovetolearnplace.com/Grammar/singularpossessives.html#anchor1845703
http://www.worksheetworks.com/english/partsofspeech/nouns/possessive-phrases.html