Collins. (2013). Work on your grammar (Advanced C1): Over 200 exercises to improve your English grammar. Tổng hợp.
Chicago ZitierstilCollins. Work On Your Grammar (Advanced C1): Over 200 Exercises to Improve Your English Grammar. Tổng hợp, 2013.
MLA ZitierstilCollins. Work On Your Grammar (Advanced C1): Over 200 Exercises to Improve Your English Grammar. Tổng hợp, 2013.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.