REPASANDO... PRESENT PERFECT SIMPLE & PRESENT PERFECT CONTINOUS

http://www.agendaweb.org/verbs/present_perfect_continuous-exercises.html
http://www.aulafacil.com/cursos/l22539/idiomas/ingles/ingles-repaso-de-gramatica/present-perfect-continuous-vs-present-perfect
https://learnenglish.britishcouncil.org/es/grammar-reference/present-perfect-simple-and-present-perfect-continuous
http://www.vitutor.com/gramatica_inglesa/verb_tense/pre_perfect_continuous.html
http://www.perfect-english-grammar.com/present-perfect-present-perfect-continuous-1.html