ONLINE PRACTICE
http://www.englisch-hilfen.de/en/exercises/if_clauses/type_1_mix.htm
http://www.englisch-hilfen.de/en/exercises/if_clauses/type_1_mix2.htm
http://www.englishpage.com/conditional/conditional1.htm
http://www.perfect-english-grammar.com/zero-conditional.html
http://www.perfect-english-grammar.com/first-conditional.html
http://www.perfect-english-grammar.com/first-conditional-exercise-1.html
