NON DEFINING RELATIVE CLAUSES

https://learnenglish.britishcouncil.org/grammar/b1-b2-grammar/relative-clauses-non-defining-relative-clauses

https://elt.oup.com/student/solutions/int/grammar/grammar_03_022e?cc=mx&selLanguage=es

https://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?04

https://www.examenglish.com/grammar/ND_relative_clauses.htm