Harrap's Easy English Dictionary
Pons

Focus Modern Business Testing 4/5

Perspectives
Hopkins

Vocabulary in Use
McCarthy, Michael u.a.

If-Clauses & Co Die Nebensätze
Groß, Achim

Dictionary of Common Errors
Heaton/Turton

Speaking Activities
Timesaver

English Grammar in Use Supplementar
Hashemi, Lousie

English Grammar 1
Henrichs-Kleinen, Ellen

On course Key
Woxbrandt / Kunze