NEGATION

http://www.classzone.com/etest/viewTestPractice.htm?testId=1310

http://www.xtec.es/~psanz/tick/exfra/B1MUL005.htm

http://babelnet.sbg.ac.at/canalreve/bravo/module8/2.1.html

http://www.didieraccord.com/exercices/index.php?ex=2.2.2.2

http://jeudeloie.free.fr/elementaire/oie.html