Vídeo com explicação: https://www.youtube.com/watch?v=lLkARyk4CTI
Link 1: http://www.grammarbank.com/relative-pronouns-exercises-1.html
Link 2: http://www.grammarbank.com/relative-clauses-examples.html
Link 3: http://www.grammarbank.com/relative-clauses-quiz.html
