FILES

PRESENT SIMPLE

https://learnenglish.britishcouncil.org/es/english-grammar/verbs/present-tense/present-simple

http://www.edufind.com/es/english-grammar/simple-present-tense/

PRESENT CONTINUOUS

https://learnenglish.britishcouncil.org/es/english-grammar/verbs/present-tense/present-continuous

PRESENT SIMPLE VS. PRESENT CONTINUOUS

http://www.englisch-hilfen.de/en/grammar/simple_present_progressive_contrasted.htm


PRESENT PERFECT

1. http://www.edufind.com/english/grammar/present_perfect.php

2. http://i.emlfiles4.com/cmpdoc/4/1/3/6/7/files/251616_g2gnov14olpgrammar.pdf?dm_i=1MVU,2XW1E,9YVALB,AM6UK,1

PAST PERFECT 

1. http://www.perfect-english-grammar.com/past-perfect.html

2. http://i.emlfiles4.com/cmpdoc/4/1/3/6/7/files/251615_g2gnov14olg.pdf?dm_i=1MVU,2XW1E,9YVALB,AM6UK,1

MAY - MIGHT - CAN - COULD - MUST

http://www.ecenglish.com/learnenglish/lessons/can-could-may-might-must


PASSIVE VOICE

http://www.myenglishpages.com/site_php_files/grammar-lesson-passive-voice.php#.VEle8yKG_kU

PAST CONTINUOUS

http://www.ego4u.com/en/cram-up/grammar/past-progressive

PAST CONTINUOUS VS. PAST SIMPLE

http://www.englisch-hilfen.de/en/grammar/simple_past_progressive_contrasted.htm

CONDITIONAL SENTENCES

http://www.ego4u.com/en/cram-up/grammar/conditional-sentences

PAST SIMPLE

http://www.edufind.com/es/english-grammar/simple-past-tense/

VERB TO BE

http://www.aprenderinglesrapidoyfacil.com/2012/08/14/aprender-el-verbo-to-be-en-ingles/