Present perfect: already, yet, just, ever, never...

http://www.clafoti.com/imagenes11/pres_perf_3.htm

http://autoenglish.org/gr.presper.i.htm

http://perso.wanadoo.es/autoenglish/gr.presper.i.htmhttp://departamentodeinglesvh.wordpress.com/3oeso/

http://aprendeinglessila.com/2013/05/presente-perfecto-just-already-yet-since-for/

http://www.universidadlaboraldemalaga.es/datos/Ingles/Present_Perfect_3.pdf

http://www.ompersonal.com.ar/ELEMENTARY/unit19/page4.htm

present perfect or past simple
montones de ejercicios yet, already, present perfect, etc
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