http://www.smic.be/smic5022/althoughdespite1.htm

http://www.smic.be/smic5022/used%20to.htm

http://www.xtec.cat/~jsuller/intermediate/multiple_choice_3_1.htm

http://www.xtec.cat/~jsuller/intermediate/multiple_choice_3_2.htm

http://www.xtec.cat/~jsuller/intermediate/multiple_choice_3_3.htm

A link for third level students.

http://a4esl.org/q/h/vm/compsup2.html

Theory:

http://www.1-language.com/englishcourse/unit66_grammar.htm

Practice:

http://a4esl.org/q/h/vm/indirectques.html

Since I can see that you have some problems with the use of the article (in both the second and the third levels), here you have a useful link to have a look at. You’ll also find some exercises to do.

http://www.englisch-hilfen.de/en/grammar/artikel.htm

http://www.usingenglish.com/quizzes/68.html

http://www.ih.hu/exercises/pre_int/g2.htm

http://www.stclaresenglish.net/langprac/winamillion.htm