Some useful links to practise Present Perfect

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

http://a4esl.org/q/h/lb/stillyet.html

http://a4esl.org/q/h/9704/bd-for-since.html

http://a4esl.org/q/h/irv004-ck.html