Relative clauses

http://speakspeak.com/english-grammar-exercises/intermediate/relative-pronouns-who-which-that-whose-when-where
http://www.learnenglishfeelgood.com/elt-adjective-clauses-mixed2.html
http://www.eltbase.com/quiz/031_02.htm
http://www.elt-els.com/2014/10/relative-pronouns-multiple-choice-test-1.html