present perfect + just, yet , already

http://www.englishexercises.org/makeagame/viewgame.asp?id=3211

http://www.english-grammar-lessons.com/presentperfect/exercise4.swf


http://www.autoenglish.org/gr.presper.i.h

http://eslzone1.tripod.com/grammarinter/_yet.htm


http://perso.wanadoo.es/autoenglish/gr.presper.i.htm

http://www.manythings.org/repeat/

http://www.eflnet.com/grammar/whquestionspresperf.p
http://www.learnenglish.be/gr2_dif2_ex1.htm

http://www.learnenglish.be/gr2_dif2_ex2.htm

http://www.learnenglish.be/gr2_dif2_ex5.htm

http://www.englishpage.com/verbpage/verbs6.h