useful websites to study conditionals

http://www.englisch-hilfen.de/en/exercises/if_clauses/type_2_statements.htm

http://www.ingilizceders.biz/if/If_Clause_Type_II.htm

http://a4esl.org/q/h/vm/if-clauses.html

http://www.english-zone.com/grammar/if-then1.html

http://www.testyourenglish.net/english-online/grammarquiz/ifsquiz.html