PRESENT PERFECT  (EXPLICACIÓN)


http://www.aprenderinglesfacil.es/2008/06/presente-perfecto-present-perfect-tense.HTML

http://www.curso-ingles.com/gramatica-inglesa/present-perfect.php

http://www.blueblocnotes.com/grammar/present-perfect/present-perfect

http://www.ego4u.com/en/cram-up/grammar/present-perfect-simple

http://www.perfect-english-grammar.com/present-perfect-exercises.HTML

http://www.englisch-hilfen.de/en/exercises/tenses/present_perfect_statements.htm

http://www.really-learn-english.com/present-perfect-exercises.HTML

http://www.agendaweb.org/verbs/present_perfect-exercises.HTML






YET, ALREADY

http://aprendeinglessila.com/2013/05/presente-perfecto-just-already-yet-since-for/

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-17335.php

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/prperf1.htm

http://www.englisch-hilfen.de/en/exercises/tenses/present_perfect_already_yet.htm

http://www.adelescorner.org/grammar/pres_perfect/pres_perfect_yet.HTML

http://www.vitutor.com/gramatica_inglesa/verb_tense/present_perfect_ej11.HTML



SINCE VS FOR


http://menuaingles.blogspot.mx/2007/02/since-for.HTML

http://ingles.about.com/od/gramatica/a/For-O-Since-Preposiciones-De-Tiempo.htm

http://www.englishexercises.org/makeagame/viewgame.asp?id=1394

http://www.agendaweb.org/grammar/for_since_already-exercises.HTML

http://www.grammarbank.com/since-vs-for-exercises.HTML

http://www.eclecticenglish.com/grammar/PresentPerfect1D.HTML

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-3647.php