FORMATION: http://www.ego4u.com/en/cram-up/grammar/present-perfect-simple/exercises
TEXT ABOUT LOCH NESS: http://www.ego4u.com/en/read-on/countries/uk/tour/loch-ness
HISTORY OF SNOWBOARDING: http://www.ego4u.com/en/read-on/animals/snowboarding?mark=preper
PRESENT PERFECT (ALREADY/ YET) : http://www.eclecticenglish.com/grammar/PresentPerfect1C.html
PRESENT PERFECT (FOR/SINCE): http://www.eclecticenglish.com/grammar/PresentPerfect1D.html
PRESENT PERFECT VERSUS PAST SIMPLE: http://www.eclecticenglish.com/grammar/PresentPerfect1E.html
http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/ppvpast1.htm
