Explanation:
1. http://www.ego4u.com/en/cram-up/grammar/simpas-preper
2. http://web2.uvcs.uvic.ca/elc/StudyZone/330/grammar/upperf.htm
3. http://www.englishtenses.com/tenses/present_perfect
Exercises:
1. http://www.autoenglish.org/gr.perf.i.htm
2. http://www.autoenglish.org/tenses/gr.perf.pdf
3. http://www.autoenglish.org/gr.since.i.htm
4. http://www.autoenglish.org/gr.since.pdf
5. http://www.englishtenses.com/quiz/present_perfect1
Video:
1. http://www.youtube.com/watch?v=JmvVPmf8zKQ&feature=youtu.be
2. http://www.youtube.com/watch?v=12wpL4CII6k&feature=youtu.be
1. http://www.ego4u.com/en/cram-up/grammar/simpas-preper
2. http://web2.uvcs.uvic.ca/elc/StudyZone/330/grammar/upperf.htm
3. http://www.englishtenses.com/tenses/present_perfect
Exercises:
1. http://www.autoenglish.org/gr.perf.i.htm
2. http://www.autoenglish.org/tenses/gr.perf.pdf
3. http://www.autoenglish.org/gr.since.i.htm
4. http://www.autoenglish.org/gr.since.pdf
5. http://www.englishtenses.com/quiz/present_perfect1
Video:
1. http://www.youtube.com/watch?v=JmvVPmf8zKQ&feature=youtu.be
2. http://www.youtube.com/watch?v=12wpL4CII6k&feature=youtu.be